1
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Paulsel TQ, Williams GJ. Current State-of-the-Art Toward Chemoenzymatic Synthesis of Polyketide Natural Products. Chembiochem 2023; 24:e202300386. [PMID: 37615926 PMCID: PMC10964317 DOI: 10.1002/cbic.202300386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 08/19/2023] [Accepted: 08/21/2023] [Indexed: 08/25/2023]
Abstract
Polyketide natural products have significant promise as pharmaceutical targets for human health and as molecular tools to probe disease and complex biological systems. While the biosynthetic logic of polyketide synthases (PKS) is well-understood, biosynthesis of designer polyketides remains challenging due to several bottlenecks, including substrate specificity constraints, disrupted protein-protein interactions, and protein solubility and folding issues. Focusing on substrate specificity, PKSs are typically interrogated using synthetic thioesters. PKS assembly lines and their products offer a wealth of information when studied in a chemoenzymatic fashion. This review provides an overview of the past two decades of polyketide chemoenzymatic synthesis and their contributions to the field of chemical biology. These synthetic strategies have successfully yielded natural product derivatives while providing critical insights into enzymatic promiscuity and mechanistic activity.
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Affiliation(s)
- Thaddeus Q Paulsel
- Department of Chemistry, NC State University Dabney Hall, Room 208, Campus Box 8204, 2620 Yarbrough Dr., NC State University, Raleigh, NC 27695, USA
- Comparative Medicine Institute, NC State University, 1060 William Moore Dr., NC State University, Raleigh, NC 27607, USA
| | - Gavin J Williams
- Department of Chemistry, NC State University Dabney Hall, Room 208, Campus Box 8204, 2620 Yarbrough Dr., NC State University, Raleigh, NC 27695, USA
- Comparative Medicine Institute, NC State University, 1060 William Moore Dr., NC State University, Raleigh, NC 27607, USA
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2
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Moor SR, Howard JR, Herrera BT, McVeigh MS, Marini F, Keatinge-Clay AT, Anslyn EV. Determination of Enantiomeric Excess and Diastereomeric Excess via Optical Methods. Application to α-methyl-β-hydroxy-carboxylic acids. Org Chem Front 2023; 10:1386-1392. [PMID: 37636898 PMCID: PMC10456989 DOI: 10.1039/d2qo01444k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
Characterization of chiral molecules in solution is paramount for measuring reaction success. However, techniques to distinguish between chiral molecules containing more than one stereocenter through the use of optical techniques remains a challenge. Herein, we report a techique using a series of circular dichroism spectra to train multivariate regression models that are capable of predicting the complete speciation of 3-hydroxy-2-methylbutanoic acid stereoisomers. From this, it is possible to rapidly and accurately determine the enantiomeric excess and diastereomeric excess of the solution without the need for chiral chromatography.
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Affiliation(s)
- Sarah R Moor
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - James R Howard
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Brenden T Herrera
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Matthew S McVeigh
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Federico Marini
- Department of Chemistry, University of Rome "La Sapienza", P.le Aldo Moro 5, Rome I-00185, Italy
| | - Adrian T Keatinge-Clay
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Eric V Anslyn
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA
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3
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Chen B, Wang F, Xie X, Liu H, Liu D, Ma L, Xiao G, Wang Q. Functional analysis of the dehydratase domains of the PUFA synthase from Emiliania huxleyi in Escherichia coli and Arabidopsis thaliana. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:123. [PMID: 36380342 PMCID: PMC9667614 DOI: 10.1186/s13068-022-02223-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Accepted: 11/04/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND Polyunsaturated fatty acid (PUFA) synthase is a multi-domain mega-enzyme that effectively synthesizes a series of PUFAs in marine microorganisms. The dehydratase (DH) domain of a PUFA synthase plays a crucial role in double bond positioning in fatty acids. Sequencing results of the coccolithophore Emiliania huxleyi (E. huxleyi, Eh) indicated that this species contains a PUFA synthase with multiple DH domains. Therefore, the current study, sought to define the functions of these DH domains (EhDHs), by cloning and overexpressing the genes encoding FabA-like EhDHs in Escherichia coli (E. coli) and Arabidopsis thaliana (A. thaliana). RESULTS A complementation test showed that the two FabA-like DH domains could restore DH function in a temperature-sensitive (Ts) mutant. Meanwhile, overexpression of FabA-like EhDH1 and EhDH2 domains increased the production of unsaturated fatty acids (UFAs) in recombinant E. coli by 43.5-32.9%, respectively. Site-directed mutagenesis analysis confirmed the authenticity of active-site residues in these domains. Moreover, the expression of tandem EhDH1-DH2 in A. thaliana altered the fatty acids content, seed weight, and germination rate. CONCLUSIONS The two FabA-like DH domains in the E. huxleyi PUFA synthase function as 3-hydroxyacyl-acyl carrier protein dehydratase in E. coli. The expression of these domains in E. coli and A. thaliana can alter the fatty acid profile in E. coli and increase the seed lipid content and germination rate in A. thaliana. Hence, introduction of DH domains controlling the dehydration process of fatty acid biosynthesis in plants might offer a new strategy to increase oil production in oilseed plants.
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Affiliation(s)
- Bihan Chen
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Feng Wang
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Xi Xie
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China.
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China.
| | - Huifan Liu
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Dongjie Liu
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Lukai Ma
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Gengsheng Xiao
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Qin Wang
- Guangdong Provincial Key Laboratory of Lingnan Specialty Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou, China
- College of Light Industry and Food, Zhongkai University of Agriculture and Engineering, Guangzhou, China
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4
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Sirirungruang S, Ad O, Privalsky TM, Ramesh S, Sax JL, Dong H, Baidoo EEK, Amer B, Khosla C, Chang MCY. Engineering site-selective incorporation of fluorine into polyketides. Nat Chem Biol 2022; 18:886-893. [PMID: 35817967 PMCID: PMC10030150 DOI: 10.1038/s41589-022-01070-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 05/23/2022] [Indexed: 02/01/2023]
Abstract
Although natural products and synthetic small molecules both serve important medicinal functions, their structures and chemical properties are relatively distinct. To expand the molecular diversity available for drug discovery, one strategy is to blend the effective attributes of synthetic and natural molecules. A key feature found in synthetic compounds that is rare in nature is the use of fluorine to tune drug behavior. We now report a method to site-selectively incorporate fluorine into complex structures to produce regioselectively fluorinated full-length polyketides. We engineered a fluorine-selective trans-acyltransferase to produce site-selectively fluorinated erythromycin precursors in vitro. We further demonstrated that these analogs could be produced in vivo in Escherichia coli on engineering of the fluorinated extender unit pool. By using engineered microbes, elaborate fluorinated compounds can be produced by fermentation, offering the potential for expanding the identification and development of bioactive fluorinated small molecules.
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Affiliation(s)
| | - Omer Ad
- Department of Chemistry, University of California, Berkeley, CA, USA
| | | | - Swetha Ramesh
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Joel L Sax
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Hongjun Dong
- Department of Chemistry, University of California, Berkeley, CA, USA
| | - Edward E K Baidoo
- Joint Bioenergy Institute, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Energy, Agile BioFoundry, Emeryville, CA, USA
| | - Bashar Amer
- Joint Bioenergy Institute, Lawrence Berkeley National Laboratory, Emeryville, CA, USA
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Chaitan Khosla
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
| | - Michelle C Y Chang
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
- Department of Chemistry, University of California, Berkeley, CA, USA.
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA.
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5
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Schröder M, Roß T, Hemmerling F, Hahn F. Studying a Bottleneck of Multimodular Polyketide Synthase Processing: the Polyketide Structure-Dependent Performance of Ketoreductase Domains. ACS Chem Biol 2022; 17:1030-1037. [PMID: 35412301 DOI: 10.1021/acschembio.2c00047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ketoreductases (KRs) are canonical domains of type I polyketide synthases (PKSs). They stereoselectively reduce ACP-bound β-ketothioester intermediates and are responsible for a large part of the stereocenters in reduced polyketides. Albeit essential for the understanding and engineering of PKS, the specific effects of altering the polyketide part of KR precursors on their performance has rarely been studied. We present investigations on the substrate-dependent performance of six isolated KR domains using a library of structurally diverse surrogates for PKS thioester intermediates. A pronounced correlation between the polyketide structure and the KR performance was observed with activity and stereoselectivity diminishing with growing deviation from the natural KR precursor structure. The extent of this decrease and the profile of arising side products was characteristic for the individual KRs. Our results reinforce the importance of structure-KR performance relationships and suggest extended studies with isolated domains and whole PKS modules.
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Affiliation(s)
- Marius Schröder
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, 95447 Bayreuth, Germany
- Biomolekulares Wirkstoffzentrum, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Theresa Roß
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, 95447 Bayreuth, Germany
| | - Franziska Hemmerling
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, 95447 Bayreuth, Germany
- Biomolekulares Wirkstoffzentrum, Leibniz Universität Hannover, 30167 Hannover, Germany
| | - Frank Hahn
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, 95447 Bayreuth, Germany
- Biomolekulares Wirkstoffzentrum, Leibniz Universität Hannover, 30167 Hannover, Germany
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6
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Thiocysteine lyases as polyketide synthase domains installing hydropersulfide into natural products and a hydropersulfide methyltransferase. Nat Commun 2021; 12:5672. [PMID: 34584078 PMCID: PMC8479088 DOI: 10.1038/s41467-021-25798-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 09/01/2021] [Indexed: 12/02/2022] Open
Abstract
Nature forms S-S bonds by oxidizing two sulfhydryl groups, and no enzyme installing an intact hydropersulfide (-SSH) group into a natural product has been identified to date. The leinamycin (LNM) family of natural products features intact S-S bonds, and previously we reported an SH domain (LnmJ-SH) within the LNM hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) assembly line as a cysteine lyase that plays a role in sulfur incorporation. Here we report the characterization of an S-adenosyl methionine (SAM)-dependent hydropersulfide methyltransferase (GnmP) for guangnanmycin (GNM) biosynthesis, discovery of hydropersulfides as the nascent products of the GNM and LNM hybrid NRPS-PKS assembly lines, and revelation of three SH domains (GnmT-SH, LnmJ-SH, and WsmR-SH) within the GNM, LNM, and weishanmycin (WSM) hybrid NRPS-PKS assembly lines as thiocysteine lyases. Based on these findings, we propose a biosynthetic model for the LNM family of natural products, featuring thiocysteine lyases as PKS domains that directly install a -SSH group into the GNM, LNM, or WSM polyketide scaffold. Genome mining reveals that SH domains are widespread in Nature, extending beyond the LNM family of natural products. The SH domains could also be leveraged as biocatalysts to install an -SSH group into other biologically relevant scaffolds. Enzymes installing an intact hydropersulfide (-SSH) group into natural products have so far not been identified. Here, the authors report the characterization of an S-adenosyl methionine-dependent hydropersulfide methyltransferase (GnmP) for guangnanmycin biosynthesis, and identification of three SH domains within several NRPS-PKS assembly lines as thiocysteine lyases.
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7
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Miyazawa T, Fitzgerald BJ, Keatinge-Clay AT. Preparative production of an enantiomeric pair by engineered polyketide synthases. Chem Commun (Camb) 2021; 57:8762-8765. [PMID: 34378565 DOI: 10.1039/d1cc03073f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Using the updated module boundary of polyketide assembly lines, modules from the pikromycin synthase were recombined into engineered synthases that furnish an enantiomeric pair of 2-stereocenter triketide lactones at >99% ee with yields up to 0.39 g per liter of E. coli K207-3 in shake flasks.
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Affiliation(s)
- Takeshi Miyazawa
- Department of Molecular Biosciences, The University of Texas at Austin, 100 E. 24th St., Austin, TX 78712, USA.
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8
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Wagner L, Roß T, Hollmann T, Hahn F. Cross-linking of a polyketide synthase domain leads to a recyclable biocatalyst for chiral oxygen heterocycle synthesis. RSC Adv 2021; 11:20248-20251. [PMID: 35479892 PMCID: PMC9033652 DOI: 10.1039/d1ra03692k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 05/26/2021] [Indexed: 12/17/2022] Open
Abstract
The potential of polyketide synthase (PKS) domains for chemoenzymatic synthesis can often not be tapped due to their low stability and activity in vitro. In this proof-of-principle study, the immobilisation of the heterocycle-forming PKS domain AmbDH3 as a cross-linked enzyme aggregate (CLEA) is described. The AmbDH3-CLEA showed good activity recovery, stability and recyclability. Repetitive reactions on the semi-preparative scale were performed with high conversion and isolated yield. Similar to that observed for the free enzyme, the aggregate retained substrate tolerance and the ability for kinetic resolution. This first example of a successful enzymatic PKS domain immobilisation demonstrates that cross-linking can in principle be applied to this type of enzyme to increase its applicability for chemoenzymatic synthesis. Cross-linking of the polyketide synthase domain AmbDH3 led to an active aggregate with improved properties for the chemoenzymatic synthesis of chiral oxygen heterocycles, such as recyclability and facile purification.![]()
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Affiliation(s)
- Lisa Wagner
- Department of Chemistry, Faculty of Biology, Chemistry and Earth Sciences, University of Bayreuth Universitätsstraße 30 95447 Bayreuth Germany
| | - Theresa Roß
- Department of Chemistry, Faculty of Biology, Chemistry and Earth Sciences, University of Bayreuth Universitätsstraße 30 95447 Bayreuth Germany
| | - Tim Hollmann
- Department of Chemistry, Faculty of Biology, Chemistry and Earth Sciences, University of Bayreuth Universitätsstraße 30 95447 Bayreuth Germany
| | - Frank Hahn
- Department of Chemistry, Faculty of Biology, Chemistry and Earth Sciences, University of Bayreuth Universitätsstraße 30 95447 Bayreuth Germany
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9
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Drufva EE, Spengler NR, Hix EG, Bailey CB. Site-Directed Mutagenesis of Modular Polyketide Synthase Ketoreductase Domains for Altered Stereochemical Control. Chembiochem 2020; 22:1122-1150. [PMID: 33185924 DOI: 10.1002/cbic.202000613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/12/2020] [Indexed: 12/18/2022]
Abstract
Bacterial modular type I polyketide synthases (PKSs) are complex multidomain assembly line proteins that produce a range of pharmaceutically relevant molecules with a high degree of stereochemical control. Due to their colinear properties, they have been considerable targets for rational biosynthetic pathway engineering. Among the domains harbored within these complex assembly lines, ketoreductase (KR) domains have been extensively studied with the goal of altering their stereoselectivity by site-directed mutagenesis, as they confer much of the stereochemical complexity present in pharmaceutically active reduced polyketide scaffolds. Here we review all efforts to date to perform site-directed mutagenesis on PKS KRs, most of which have been done in the context of excised KR domains on model diffusible substrates such as β-keto N-acetyl cysteamine thioesters. We also discuss the challenges around translating the findings of these studies to alter stereocontrol in the context of a complex multidomain enzymatic assembly line.
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Affiliation(s)
- Erin E Drufva
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Nolan R Spengler
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Elijah G Hix
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
| | - Constance B Bailey
- Department of Chemistry, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
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10
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Wunderlich J, Roß T, Schröder M, Hahn F. Step-Economic Synthesis of Biomimetic β-Ketopolyene Thioesters and Demonstration of Their Usefulness in Enzymatic Biosynthesis Studies. Org Lett 2020; 22:4955-4959. [PMID: 32610930 DOI: 10.1021/acs.orglett.0c01348] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies on the biosynthetic processing of polyene thioester intermediates are complicated by limited access to appropriate substrate surrogates. We present a step-economic synthetic access to biomimetic β-ketopolyene thioesters that is based on an Ir-catalyzed reductive Horner-Wadsworth-Emmons olefination. New β-ketotriene and pentaenethioates of pantetheine and N-acetylcysteamine were exemplarily synthesized via short and concise routes. The usefulness of these compounds was demonstrated in an in vitro assay with the ketoreductase domain MycKRB from mycolactone biosynthesis.
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Affiliation(s)
- Johannes Wunderlich
- Fakultät Biologie, Chemie und Geologie, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Theresa Roß
- Fakultät Biologie, Chemie und Geologie, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Marius Schröder
- Fakultät Biologie, Chemie und Geologie, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Frank Hahn
- Fakultät Biologie, Chemie und Geologie, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
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11
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Zhang Z, Cepeda AJ, Robles ML, Hirsch M, Kumru K, Zhou JA, Keatinge-Clay AT. General chemoenzymatic route to two-stereocenter triketides employing assembly line ketoreductases. Chem Commun (Camb) 2019; 56:157-160. [PMID: 31799975 DOI: 10.1039/c9cc07966a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Modular polyketide synthases (PKSs) are enzymatic assembly lines that fuse carbon fragments into complex chiral products. Here, their synthetic logic is employed to chemoenzymatically generate two-stereocenter triketides. Each of the four stereoisomers was constructed in a stereocontrolled manner using C-acylation and two PKS ketoreductases possessing opposite stereoselectivities.
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Affiliation(s)
- Zhicheng Zhang
- Department of Chemistry, The University of Texas at Austin, 100 E. 24th St., Austin, TX 78712, USA
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12
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Morlighem JÉRL, Radis-Baptista G. The Place for Enzymes and Biologically Active Peptides from Marine Organisms for Application in Industrial and Pharmaceutical Biotechnology. Curr Protein Pept Sci 2019; 20:334-355. [PMID: 30255754 DOI: 10.2174/1389203719666180926121722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/10/2018] [Accepted: 09/15/2018] [Indexed: 01/07/2023]
Abstract
Since the beginning of written history, diverse texts have reported the use of enzymatic preparations in food processing and have described the medicinal properties of crude and fractionated venoms to treat various diseases and injuries. With the biochemical characterization of enzymes from distinct sources and bioactive polypeptides from animal venoms, the last sixty years have testified the advent of industrial enzymology and protein therapeutics, which are currently applicable in a wide variety of industrial processes, household products, and pharmaceuticals. Bioprospecting of novel biocatalysts and bioactive peptides is propelled by their unsurpassed properties that are applicable for current and future green industrial processes, biotechnology, and biomedicine. The demand for both novel enzymes with desired characteristics and novel peptides that lead to drug development, has experienced a steady increase in response to the expanding global market for industrial enzymes and peptidebased drugs. Moreover, although largely unexplored, oceans and marine realms, with their unique ecosystems inhabited by a large variety of species, including a considerable number of venomous animals, are recognized as untapped reservoirs of molecules and macromolecules (enzymes and bioactive venom-derived peptides) that can potentially be converted into highly valuable biopharmaceutical products. In this review, we have focused on enzymes and animal venom (poly)peptides that are presently in biotechnological use, and considering the state of prospection of marine resources, on the discovery of useful industrial biocatalysts and drug leads with novel structures exhibiting selectivity and improved performance.
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Affiliation(s)
- Jean-Étienne R L Morlighem
- Institute for Marine Sciences, Federal University of Ceara, Av da Abolicao 3207. Fortaleza/CE. 60165081, Brazil
| | - Gandhi Radis-Baptista
- Institute for Marine Sciences, Federal University of Ceara, Av da Abolicao 3207. Fortaleza/CE. 60165081, Brazil
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13
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Herrera BT, Moor SR, McVeigh M, Roesner EK, Marini F, Anslyn EV. Rapid Optical Determination of Enantiomeric Excess, Diastereomeric Excess, and Total Concentration Using Dynamic-Covalent Assemblies: A Demonstration Using 2-Aminocyclohexanol and Chemometrics. J Am Chem Soc 2019; 141:11151-11160. [PMID: 31251589 DOI: 10.1021/jacs.9b03844] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Optical analysis of reaction parameters such as enantiomeric excess (ee), diastereomeric excess (de), and yield are becoming increasingly useful as assays for differing functional groups become available. These assays typically exploit reversible covalent or noncovalent assemblies that impart optical signals, commonly circular dichroism (CD), that are indicative of the stereochemistry and ee at a stereocenter proximal to the functional group of interest. Very few assays have been reported that determine ee and de when two stereocenters are present, and none have targeted two different functional groups that are vicinal and lack chromophores entirely. Using a CD assay that targets chiral secondary alcohols, a separate CD assay for chiral primary amines, a UV-vis assay for de, and a fluorescence assay for concentration, we demonstrate a work-flow for speciation of the enantiomers and diastereomers of 2-aminocyclohexanol as a test-bed analyte. Because of the fact the functional groups are vicinal, we found that the ee determination at the two stereocenters is influenced by the adjacent center, and this led us to implement a chemometric patterning approach, resulting in a 4% absolute error in full speciation of the four stereoisomers. The procedure presented herein would allow for the total speciation of around 96 reactions in 27 min using a high-throughput experimentation routine. While 2-aminocyclohexanol is used to demonstrate the methods, the general workflow should be amenable to analysis of other stereoisomers when two stereocenters are present.
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Affiliation(s)
- Brenden T Herrera
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Sarah R Moor
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Matthew McVeigh
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Emily K Roesner
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Federico Marini
- Department of Chemistry , University of Rome "La Sapienza" , P.le Aldo Moro 5 , Rome I-00185 , Italy
| | - Eric V Anslyn
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
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14
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Herrera BT, Lin CY, Wright AM, Moor SR, Anslyn EV. Mathematical Relationships of Individual Stereocenter er Values to dr Values. J Org Chem 2019; 84:5922-5926. [PMID: 30925217 DOI: 10.1021/acs.joc.9b00447] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
A mathematical relationship is derived for relating the enantiomeric ratios (er values) of two individual stereocenters within a single chiral molecule to the diastereomeric ratio (dr). Whereas the er (or enantiomeric excess, ee) of chiral molecules is readily determined by chiral chromatography and dr values can be determined by chromatography or NMR, modern methods for the optical determination of er values at individual functional groups do not normally determine the er and dr of the entire molecule. We find there is only a special circumstance when knowledge of the er of two individual stereocenters can be used to predict the er of the enantiomers in each diastereomeric set, along with the dr of the stereoisomers. Under circumstances where this relationship fails, one will require a dr assay in addition to two individual er assays to fully characterize the stereochemical parameters of a reaction. Thus, with these circumstances in mind, we give mathematical relationships for determining complete stereoisomer speciation having the knowledge of individual stereocenter er values and a dr value.
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Affiliation(s)
- Brenden T Herrera
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Chung-Yon Lin
- Department of Molecular Medicine , Scripps Research Institute , La Jolla , California 92037 , United States
| | - Alexandra M Wright
- Office of the Registrar , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Sarah R Moor
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Eric V Anslyn
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
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15
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Xie X, Cane DE. pH-Rate profiles establish that polyketide synthase dehydratase domains utilize a single-base mechanism. Org Biomol Chem 2019; 16:9165-9170. [PMID: 30457629 DOI: 10.1039/c8ob02637h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
FosDH1 from module 1 of the fostriecin polyketide synthase (PKS) catalyzes the dehydration of a 3-hydroxybutyryl-SACP to the (E)-3-butenoyl-SACP. The steady-state kinetic parameters, kcat and kcat/Km, were determined over the pH range 3.0 to 9.2 for the FosDH1-catalyzed dehydration of the N-acetycsteamine thioester, 3-hydroxybutyryl-SNAC (3), to (E)-3-butenoyl-SNAC (4). The pH rate profiles for both log(kcat) and log(kcat/Km) each corresponded to a single pH-dependent ionization to give an active site general base, with a calculated pKa 6.1 ± 0.2 for kcat and pKa 5.7 ± 0.1 for kcat/Km. These results are inconsistent with the commonly suggested "two-base" (base-acid) mechanism for the dehydratases of PKS and fatty acid biosynthesis and support a simple one-base mechanism in which the universally conserved active site His residue acts as the base to deprotonate C-2 of the substrate, then redonates the proton to the C-3 hydroxyl group to promote C-O bond-cleavage and elimination of water. The carboxylate of the paired Asp or Glu residue is thought to bind and orient the hydroxyl group of the substrate in the stereoelectonically favored conformation.
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Affiliation(s)
- Xinqiang Xie
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108, USA.
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16
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Häckh M, Lucas X, Marolt M, Leadlay PF, Müller M, Günther S, Lüdeke S. Hidden Specificities in Enzyme Catalysis: Structural Basis of Substrate Structure‐Selectivity Relationship of a Ketoreductase. Chembiochem 2019; 20:1150-1154. [DOI: 10.1002/cbic.201800799] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Matthias Häckh
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
| | - Xavier Lucas
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
- Present addressRoche Pharma Research and Early DevelopmentRoche Innovation Center 4070 Basel Switzerland
| | - Marija Marolt
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
| | - Peter F. Leadlay
- Department of BiochemistryUniversity of Cambridge 80 Tennis Court Road Cambridge CB2 1GA UK
| | - Michael Müller
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
| | - Stefan Günther
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
| | - Steffen Lüdeke
- Institute of Pharmaceutical SciencesUniversity of Freiburg Albertstrasse 25 79104 Freiburg Germany
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17
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Valencia LE, Zhang Z, Cepeda AJ, Keatinge-Clay AT. Seven-enzyme in vitro cascade to (3R)-3-hydroxybutyryl-CoA. Org Biomol Chem 2019; 17:1375-1378. [PMID: 30652175 DOI: 10.1039/c8ob02858c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Economical and environmentally-friendly routes to convert feedstock chemicals like acetate into valuable chiral products such as (R)-3-hydroxybutyrate are in demand. Here, seven enzymes (CoaA, CoaD, CoaE, ACS, BktB, PhaB, and GDH) are employed in a one-pot, in vitro, biocatalytic synthesis of (3R)-3-hydroxybutyryl-CoA, which was readily isolated. This platform generates not only chiral diketide building blocks but also desirable CoA derivatives.
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Affiliation(s)
- Luis E Valencia
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA.
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18
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Ronnebaum TA, McFarlane JS, Prisinzano TE, Booker SJ, Lamb AL. Stuffed Methyltransferase Catalyzes the Penultimate Step of Pyochelin Biosynthesis. Biochemistry 2018; 58:665-678. [PMID: 30525512 DOI: 10.1021/acs.biochem.8b00716] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Nonribosomal peptide synthetases use tailoring domains to incorporate chemical diversity into the final natural product. A structurally unique set of tailoring domains are found to be stuffed within adenylation domains and have only recently begun to be characterized. PchF is the NRPS termination module in pyochelin biosynthesis and includes a stuffed methyltransferase domain responsible for S-adenosylmethionine (AdoMet)-dependent N-methylation. Recent studies of stuffed methyltransferase domains propose a model in which methylation occurs on amino acids after adenylation and thiolation rather than after condensation to the nascent peptide chain. Herein, we characterize the adenylation and stuffed methyltransferase didomain of PchF through the synthesis and use of substrate analogues, steady-state kinetics, and onium chalcogen effects. We provide evidence that methylation occurs through an SN2 reaction after thiolation, condensation, cyclization, and reduction of the module substrate cysteine and is the penultimate step in pyochelin biosynthesis.
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Affiliation(s)
| | | | | | - Squire J Booker
- Department of Chemistry, Department of Biochemistry and Molecular Biology, and the Howard Hughes Medical Institute , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
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19
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Meinke JL, Mehaffey MR, Wagner DT, Sun N, Zhang Z, Brodbelt JS, Keatinge-Clay AT. Structural and Functional Studies of a gem-Dimethylating Methyltransferase from a trans-Acyltransferase Assembly Line. ACS Chem Biol 2018; 13:3306-3314. [PMID: 30371052 DOI: 10.1021/acschembio.8b00733] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The methyl substituents in products of trans-acyltransferase assembly lines are usually incorporated by S-adenosyl-methionine (SAM)-dependent methyltransferase (MT) domains. The gem-dimethyl moieties within the polyketide disorazol are installed through the iterative action of an MT in the third module of its assembly line. The 1.75-Å-resolution crystal structure of this MT helps elucidate how it catalyzes the addition of two methyl groups. Activity assays of point mutants on β-ketoacyl chains linked to an acyl carrier protein and N-acetylcysteamine provide additional insights into the roles of active site residues. The replacement of an alanine with a phenylalanine at an apparent gatekeeping position resulted in more monomethylation than dimethylation. MTs may form an interface with ketoreductases (KRs) and even mediate the docking of trans-acyltransferase assembly line polypeptides through this association.
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Affiliation(s)
- Jessica L. Meinke
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - M. Rachel Mehaffey
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Drew T. Wagner
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ningze Sun
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Zhicheng Zhang
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S. Brodbelt
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Adrian T. Keatinge-Clay
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
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20
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Liu C, Yuan M, Xu X, Wang L, Keatinge-Clay AT, Deng Z, Lin S, Zheng J. Substrate-bound structures of a ketoreductase from amphotericin modular polyketide synthase. J Struct Biol 2018; 203:135-141. [PMID: 29626512 DOI: 10.1016/j.jsb.2018.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 03/30/2018] [Accepted: 04/03/2018] [Indexed: 11/29/2022]
Abstract
Ketoreductase (KR) domains of modular polyketide synthases (PKSs) control the stereochemistry of C2 methyl and C3 hydroxyl substituents of polyketide intermediates. To understand the molecular basis of stereocontrol exerted by KRs, the crystal structure of a KR from the second module of the amphotericin PKS (AmpKR2) complexed with NADP+ and 2-methyl-3-oxopentanoyl-pantetheine was solved. This first ternary structure provides direct evidence to the hypothesis that a substrate enters into the active site of an A-type KR from the side opposite the coenzyme to generate an L-hydroxyl substituent. A comparison with the ternary complex of a G355T/Q364H mutant sheds light on the structural basis for stereospecificity toward the substrate C2 methyl substituent. Functional assays suggest the pantetheine handle shows obvious influence on the catalytic efficiency and the stereochemical outcome. Together, these findings extend our current understanding of the stereochemical control of PKS KR domains.
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Affiliation(s)
- Chenguang Liu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Meijuan Yuan
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xu Xu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lei Wang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Adrian T Keatinge-Clay
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shuangjun Lin
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jianting Zheng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
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21
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Structural and Functional Trends in Dehydrating Bimodules from trans-Acyltransferase Polyketide Synthases. Structure 2017; 25:1045-1055.e2. [PMID: 28625788 PMCID: PMC5553570 DOI: 10.1016/j.str.2017.05.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 05/04/2017] [Accepted: 05/15/2017] [Indexed: 01/07/2023]
Abstract
In an effort to uncover the structural motifs and biosynthetic logic of the relatively uncharacterized trans-acyltransferase polyketide synthases, we have begun the dissection of the enigmatic dehydrating bimodules common in these enzymatic assembly lines. We report the 1.98 Å resolution structure of a ketoreductase (KR) from the first half of a type A dehydrating bimodule and the 2.22 Å resolution structure of a dehydratase (DH) from the second half of a type B dehydrating bimodule. The KR, from the third module of the bacillaene synthase, and the DH, from the tenth module of the difficidin synthase, possess features not observed in structurally characterized homologs. The DH architecture provides clues for how it catalyzes a unique double dehydration. Correlations between the chemistries proposed for dehydrating bimodules and bioinformatic analysis indicate that type A dehydrating bimodules generally produce an α/β-cis alkene moiety, while type B dehydrating bimodules generally produce an α/β-trans, γ/δ-cis diene moiety.
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22
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Xie X, Garg A, Khosla C, Cane DE. Mechanism and Stereochemistry of Polyketide Chain Elongation and Methyl Group Epimerization in Polyether Biosynthesis. J Am Chem Soc 2017; 139:3283-3292. [PMID: 28157306 DOI: 10.1021/jacs.7b00278] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The polyketide synthases responsible for the biosynthesis of the polyether antibiotics nanchangmycin (1) and salinomycin (4) harbor a number of redox-inactive ketoreductase (KR0) domains that are implicated in the generation of C2-epimerized (2S)-2-methyl-3-ketoacyl-ACP intermediates. Evidence that the natural substrate for the polyether KR0 domains is, as predicted, a (2R)-2-methyl-3-ketoacyl-ACP intermediate, came from a newly developed coupled ketosynthase (KS)-ketoreductase (KR) assay that established that the decarboxylative condensation of methylmalonyl-CoA with S-propionyl-N-acetylcysteamine catalyzed by the Nan[KS1][AT1] didomain from module 1 of the nanchangmycin synthase generates exclusively the corresponding (2R)-2-methyl-3-ketopentanoyl-ACP (7a) product. In tandem equilibrium isotope exchange experiments, incubation of [2-2H]-(2R,3S)-2-methyl-3-hydroxypentanoyl-ACP (6a) with redox-active, epimerase-inactive EryKR6 from module 6 of the 6-deoxyerythronolide B synthase and catalytic quantities of NADP+ in the presence of redox-inactive, recombinant NanKR10 or NanKR50, from modules 1 and 5 of the nanchangmycin synthase, or recombinant SalKR70 from module 7 of the salinomycin synthase, resulted in first-order, time-dependent washout of deuterium from 6a. Control experiments confirmed that this washout was due to KR0-catalyzed isotope exchange of the reversibly generated, transiently formed oxidation product [2-2H]-(2R)-2-methyl-3-ketopentanoyl-ACP (7a), consistent with the proposed epimerase activity of each of the KR0 domains. Although they belong to the superfamily of short chain dehydrogenase-reductases, the epimerase-active KR0 domains from polyether synthases lack one or both residues of the conserved Tyr-Ser dyad that has previously been implicated in KR-catalyzed epimerizations.
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Affiliation(s)
- Xinqiang Xie
- Department of Chemistry, Brown University , Box H, Providence, Rhode Island 02912-9108, United States
| | - Ashish Garg
- Department of Chemistry, Brown University , Box H, Providence, Rhode Island 02912-9108, United States
| | - Chaitan Khosla
- Departments of Chemical Engineering, Chemistry, and Biochemistry, Stanford University , Stanford, California 94305, United States
| | - David E Cane
- Department of Chemistry, Brown University , Box H, Providence, Rhode Island 02912-9108, United States
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23
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Franke J, Hertweck C. Biomimetic Thioesters as Probes for Enzymatic Assembly Lines: Synthesis, Applications, and Challenges. Cell Chem Biol 2016; 23:1179-1192. [PMID: 27693058 DOI: 10.1016/j.chembiol.2016.08.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/09/2016] [Accepted: 08/31/2016] [Indexed: 10/20/2022]
Abstract
Thioesters play essential roles in many biosynthetic pathways to fatty acids, esters, polyketides, and non-ribosomal peptides. Coenzyme A (CoA) and related phosphopantetheine thioesters are typically employed as activated acyl units for diverse C-C, C-O, and C-N coupling reactions. To study and control these enzymatic assembly lines in vitro and in vivo structurally simplified analogs such as N-acetylcysteamine (NAC) thioesters have been developed. This review gives an overview on experimental strategies enabled by synthetic NAC thioesters, such as the elucidation of complex biosynthetic pathways and enzyme mechanisms as well as precursor-directed biosynthesis and mutasynthesis. The review also summarizes synthetic protocols and protection group strategies to access these versatile synthetic tools, which are reactive and often unstable compounds. In addition, alternative phosphopantetheine thioester mimics are presented that can be used as protein tags or suicide inhibitors for protein crosslinking and off-loading probes to elucidate polyketide intermediates.
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Affiliation(s)
- Jakob Franke
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745 Jena, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstraße 11a, 07745 Jena, Germany; Friedrich Schiller University, 07743 Jena, Germany.
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24
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Methyltransferases excised from trans-AT polyketide synthases operate on N-acetylcysteamine-bound substrates. J Antibiot (Tokyo) 2016; 69:567-570. [PMID: 27301661 PMCID: PMC4963292 DOI: 10.1038/ja.2016.66] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/02/2016] [Accepted: 05/08/2016] [Indexed: 12/20/2022]
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25
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Parages ML, Gutiérrez-Barranquero JA, Reen FJ, Dobson ADW, O'Gara F. Integrated (Meta) Genomic and Synthetic Biology Approaches to Develop New Biocatalysts. Mar Drugs 2016; 14:E62. [PMID: 27007381 PMCID: PMC4810074 DOI: 10.3390/md14030062] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 02/18/2016] [Accepted: 03/11/2016] [Indexed: 12/21/2022] Open
Abstract
In recent years, the marine environment has been the subject of increasing attention from biotechnological and pharmaceutical industries as a valuable and promising source of novel bioactive compounds. Marine biodiscovery programmes have begun to reveal the extent of novel compounds encoded within the enormous bacterial richness and diversity of the marine ecosystem. A combination of unique physicochemical properties and spatial niche-specific substrates, in wide-ranging and extreme habitats, underscores the potential of the marine environment to deliver on functionally novel biocatalytic activities. With the growing need for green alternatives to industrial processes, and the unique transformations which nature is capable of performing, marine biocatalysts have the potential to markedly improve current industrial pipelines. Furthermore, biocatalysts are known to possess chiral selectivity and specificity, a key focus of pharmaceutical drug design. In this review, we discuss how the explosion in genomics based sequence analysis, allied with parallel developments in synthetic and molecular biology, have the potential to fast-track the discovery and subsequent improvement of a new generation of marine biocatalysts.
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Affiliation(s)
- María L Parages
- BIOMERIT Research Centre, School of Microbiology, University College Cork, National University of Ireland, Cork, Ireland.
| | - José A Gutiérrez-Barranquero
- BIOMERIT Research Centre, School of Microbiology, University College Cork, National University of Ireland, Cork, Ireland.
| | - F Jerry Reen
- BIOMERIT Research Centre, School of Microbiology, University College Cork, National University of Ireland, Cork, Ireland.
| | - Alan D W Dobson
- School of Microbiology, University College Cork, Cork, Ireland.
| | - Fergal O'Gara
- BIOMERIT Research Centre, School of Microbiology, University College Cork, National University of Ireland, Cork, Ireland.
- School of Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth WA 6845, Australia.
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26
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Eng CH, Yuzawa S, Wang G, Baidoo EEK, Katz L, Keasling JD. Alteration of Polyketide Stereochemistry from anti to syn by a Ketoreductase Domain Exchange in a Type I Modular Polyketide Synthase Subunit. Biochemistry 2016; 55:1677-80. [DOI: 10.1021/acs.biochem.6b00129] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Clara H. Eng
- Synthetic Biology Engineering Research Center, 5885 Hollis Street, Emeryville, California 94608, United States
| | | | - George Wang
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, United States
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, United States
| | - Edward E. K. Baidoo
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, United States
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, United States
| | - Leonard Katz
- Synthetic Biology Engineering Research Center, 5885 Hollis Street, Emeryville, California 94608, United States
| | - Jay D. Keasling
- Synthetic Biology Engineering Research Center, 5885 Hollis Street, Emeryville, California 94608, United States
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, United States
- Biological
Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, United States
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27
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Xie X, Garg A, Keatinge-Clay AT, Khosla C, Cane DE. Epimerase and Reductase Activities of Polyketide Synthase Ketoreductase Domains Utilize the Same Conserved Tyrosine and Serine Residues. Biochemistry 2016; 55:1179-86. [PMID: 26863427 DOI: 10.1021/acs.biochem.6b00024] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of the conserved active site tyrosine and serine residues in epimerization catalyzed by polyketide synthase ketoreductase (PKS KR) domains has been investigated. Both mutant and wild-type forms of epimerase-active KR domains, including the intrinsically redox-inactive EryKR3° and PicKR3° as well as redox-inactive mutants of EryKR1, were incubated with [2-(2)H]-(2R,3S)-2-methyl-3-hydroxypentanoyl-SACP ([2-(2)H]-2) and 0.05 equiv of NADP(+) in the presence of the redox-active, epimerase-inactive EryKR6 domain. The residual epimerase activity of each mutant was determined by tandem equilibrium isotope exchange, in which the first-order, time-dependent washout of isotope from 2 was monitored by liquid chromatography-tandem mass spectrometry with quantitation of the deuterium content of the diagnostic pantetheinate ejection fragment (4). Replacement of the active site Tyr or Ser residues, alone or together, significantly reduced the observed epimerase activity of each KR domain with minimal effect on substrate binding. Our results demonstrate that the epimerase and reductase activities of PKS KR domains share a common active site, with both reactions utilizing the same pair of Tyr and Ser residues.
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Affiliation(s)
- Xinqiang Xie
- Department of Chemistry, Box H, Brown University , Providence, Rhode Island 02912-9108, United States
| | - Ashish Garg
- Department of Chemistry, Box H, Brown University , Providence, Rhode Island 02912-9108, United States
| | - Adrian T Keatinge-Clay
- Departments of Molecular Biosciences and Chemistry, The University of Texas at Austin , 1 University Station A5300, Austin, Texas 78712-0165, United States
| | - Chaitan Khosla
- Departments of Chemical Engineering, Chemistry, and Biochemistry, Stanford University , Stanford, California 94305, United States
| | - David E Cane
- Department of Chemistry, Box H, Brown University , Providence, Rhode Island 02912-9108, United States
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28
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Bailey CB, Pasman ME, Keatinge-Clay AT. Substrate structure-activity relationships guide rational engineering of modular polyketide synthase ketoreductases. Chem Commun (Camb) 2016; 52:792-5. [PMID: 26568113 PMCID: PMC4690787 DOI: 10.1039/c5cc07315d] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Modular polyketide synthase ketoreductases can set two chiral centers through a single reduction. To probe the basis of stereocontrol, a structure-activity relationship study was performed with three α-methyl, β-ketothioester substrates and four ketoreductases. Since interactions with the β-ketoacyl moiety were found to be most critical, residues implicated in contacting this moiety were mutated. Two mutations were sufficient to completely reverse the stereoselectivity of the model ketoreductase EryKR1, converting it from an enzyme that generates (2S,3R)-products into one that yields (2S,3S)-products.
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Affiliation(s)
- Constance B Bailey
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA.
| | - Marjolein E Pasman
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA.
| | - Adrian T Keatinge-Clay
- Department of Chemistry, University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, TX 78712, USA. and Department of Molecular Biosciences, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA
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29
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Cacho RA, Thuss J, Xu W, Sanichar R, Gao Z, Nguyen A, Vederas JC, Tang Y. Understanding Programming of Fungal Iterative Polyketide Synthases: The Biochemical Basis for Regioselectivity by the Methyltransferase Domain in the Lovastatin Megasynthase. J Am Chem Soc 2015; 137:15688-91. [PMID: 26630357 DOI: 10.1021/jacs.5b11814] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Highly reducing polyketide synthases (HR-PKSs) from fungi synthesize complex natural products using a single set of domains in a highly programmed, iterative fashion. The most enigmatic feature of HR-PKSs is how tailoring domains function selectively during different iterations of chain elongation to afford structural diversity. Using the lovastatin nonaketide synthase LovB as a model system and a variety of acyl substrates, we characterized the substrate specificity of the LovB methyltransferase (MT) domain. We showed that, while the MT domain displays methylation activity toward different β-ketoacyl groups, it is exceptionally selective toward its naturally programmed β-keto-dienyltetraketide substrate with respect to both chain length and functionalization. Accompanying characterization of the ketoreductase (KR) domain displays broader substrate specificity toward different β-ketoacyl groups. Our studies indicate that selective modifications by tailoring domains, such as the MTs, are achieved by higher kinetic efficiency on a particular substrate relative to the rate of transformation by other competing domains.
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Affiliation(s)
- Ralph A Cacho
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Justin Thuss
- Department of Chemistry, University of Alberta , Edmonton, AB T6G 2G2, Canada
| | - Wei Xu
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - Randy Sanichar
- Department of Chemistry, University of Alberta , Edmonton, AB T6G 2G2, Canada
| | - Zhizeng Gao
- Department of Chemistry, University of Alberta , Edmonton, AB T6G 2G2, Canada
| | - Allison Nguyen
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
| | - John C Vederas
- Department of Chemistry, University of Alberta , Edmonton, AB T6G 2G2, Canada
| | - Yi Tang
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States
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30
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Fage CD, Meinke JL, Keatinge-Clay AT. Coenzyme A-free activity, crystal structure, and rational engineering of a promiscuous β-ketoacyl thiolase from Ralstonia eutropha. ACTA ACUST UNITED AC 2015; 121:113-121. [PMID: 26494979 DOI: 10.1016/j.molcatb.2015.08.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Thiolases catalyze the formation of carbon-carbon bonds in diverse biosynthetic pathways. The promiscuous β-ketoacyl thiolase B of Ralstonia eutropha (ReBktB) has been utilized in the in vivo conversion of Coenzyme A (CoA)-linked precursors such as acetyl-CoA and glycolyl-CoA into β-hydroxy acids, including the pharmaceutically-important 3,4-dihydroxybutyric acid. Such thiolases could serve as powerful carbon-carbon bond-forming biocatalysts in vitro if handles less costly than CoA were employable. Here, thiolase activity is demonstrated toward substrates linked to the readily-available CoA mimic, N-acetylcysteamine (NAC). ReBktB was observed to catalyze the retro-Claisen condensation of several β-ketoacyl-S-NAC substrates, with a preference for 3-oxopentanoyl-S-NAC over 3-oxobutanoyl-, 3-oxohexanoyl-, and 3-oxoheptanoyl-S-NAC. A 2.0 Å-resolution crystal structure, in which the asymmetric unit consists of four ReBktB tetramers, provides insight into acyl group specificity and how it may be engineered. By replacing an active site methionine with an alanine, a mutant possessing significant activity towards α-methyl substituted, NAC-linked substrates was engineered. The ability of ReBktB and its engineered mutants to utilize NAC-linked substrates will facilitate the in vitro biocatalytic synthesis of diketide chiral building blocks from feedstock molecules such as acetate and propionate.
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Affiliation(s)
- Christopher D Fage
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, USA
| | - Jessica L Meinke
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, USA
| | - Adrian T Keatinge-Clay
- Department of Molecular Biosciences, The University of Texas, Austin, TX 78712, USA. ; Department of Chemistry, The University of Texas, Austin, TX 78712, USA
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31
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Fiers WD, Dodge GJ, Li Y, Smith JL, Fecik RA, Aldrich CC. Tylosin polyketide synthase module 3: stereospecificity, stereoselectivity and steady-state kinetic analysis of β-processing domains via diffusible, synthetic substrates. Chem Sci 2015; 6:5027-5033. [PMID: 26366283 PMCID: PMC4540058 DOI: 10.1039/c5sc01505g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 06/11/2015] [Indexed: 01/01/2023] Open
Abstract
Natural and modified substrates coupled with LC-MS/MS analysis of products revealed the stereospecificity and stereoselectivity of a polyketide didomain.
Polyketide synthase (PKS) β-processing domains are responsible for much of the stereochemical complexity of polyketide natural products. Although the importance of β-processing domains has been well noted and significantly explored, key stereochemical details pertaining to cryptic stereochemistry and the impact of remote stereogenic centers have yet to be fully discerned. To uncover the inner workings of ketoreductases (KR) and dehydratases (DH) from the tylosin pathway a didomain composed of TylDH3-KR3 was recombinantly expressed and interrogated with full-length tetraketide substrates to probe the impact of vicinal and distal stereochemistry. In vitro product isolation analysis revealed the products of the cryptic KR as d-alcohols and of the DH as trans-olefins. Steady-state kinetic analysis of the dehydration reaction demonstrated a strict stereochemical tolerance at the β-position as d-configured substrates were processed more than 100 times more efficiently than l-alcohols. Unexpectedly, the kcat/KM values were diminished 14- to 45-fold upon inversion of remote ε- and ζ-stereocenters. This stereochemical discrimination is predicted to be driven by a combination of allylic A1,3 strain that likely disfavors binding of the ε-epimer and a loss of electrostatic interactions with the ζ-epimer. Our results strongly suggest that dehydratases may play a role in refining the stereochemical outcomes of preceding modules through their substrate stereospecificity, honing the configurational purity of the final PKS product.
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Affiliation(s)
- William D Fiers
- Department of Medicinal Chemistry , College of Pharmacy , University of Minnesota , Minneapolis , Minnesota 55455 , USA . ;
| | - Greg J Dodge
- Department of Biological Chemistry and Life Sciences Institute , University of Michigan , Ann Arbor , Michigan 48109 , USA
| | - Yang Li
- Department of Medicinal Chemistry , College of Pharmacy , University of Minnesota , Minneapolis , Minnesota 55455 , USA . ;
| | - Janet L Smith
- Department of Biological Chemistry and Life Sciences Institute , University of Michigan , Ann Arbor , Michigan 48109 , USA
| | - Robert A Fecik
- Department of Medicinal Chemistry , College of Pharmacy , University of Minnesota , Minneapolis , Minnesota 55455 , USA . ;
| | - Courtney C Aldrich
- Department of Medicinal Chemistry , College of Pharmacy , University of Minnesota , Minneapolis , Minnesota 55455 , USA . ;
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32
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Wang F, Wang Y, Ji J, Zhou Z, Yu J, Zhu H, Su Z, Zhang L, Zheng J. Structural and functional analysis of the loading acyltransferase from avermectin modular polyketide synthase. ACS Chem Biol 2015; 10:1017-25. [PMID: 25581064 DOI: 10.1021/cb500873k] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The loading acyltransferase (AT) domains of modular polyketide synthases (PKSs) control the choice of starter units incorporated into polyketides and are therefore attractive targets for the engineering of modular PKSs. Here, we report the structural and biochemical characterizations of the loading AT from avermectin modular PKS, which accepts more than 40 carboxylic acids as alternative starter units for the biosynthesis of a series of congeners. This first structural analysis of loading ATs from modular PKSs revealed the molecular basis for the relaxed substrate specificity. Residues important for substrate binding and discrimination were predicted by modeling a substrate into the active site. A mutant with altered specificity toward a panel of synthetic substrate mimics was generated by site-directed mutagenesis of the active site residues. The hydrolysis of the N-acetylcysteamine thioesters of racemic 2-methylbutyric acid confirmed the stereospecificity of the avermectin loading AT for an S configuration at the C-2 position of the substrate. Together, these results set the stage for region-specific modification of polyketides through active site engineering of loading AT domains of modular PKSs.
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Affiliation(s)
- Fen Wang
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Yanjie Wang
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Junjie Ji
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Zhan Zhou
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Jingkai Yu
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Hua Zhu
- CAS
Key Laboratory of Pathogenic Microbiology and Immunology, Institute
of Microbiology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Zhiguo Su
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Lixin Zhang
- CAS
Key Laboratory of Pathogenic Microbiology and Immunology, Institute
of Microbiology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Jianting Zheng
- National
Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
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33
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Mugnai ML, Shi Y, Keatinge-Clay AT, Elber R. Molecular dynamics studies of modular polyketide synthase ketoreductase stereospecificity. Biochemistry 2015; 54:2346-59. [PMID: 25835227 DOI: 10.1021/bi501401g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ketoreductases (KRs) from modular polyketide synthases (PKSs) can perform stereospecific catalysis, selecting a polyketide with a D- or L-α-methyl substituent for NADPH-mediated reduction. In this report, molecular dynamics (MD) simulations were performed to investigate the interactions that control stereospecificity. We studied the A1-type KR from the second module of the amphotericin PKS (A1), which is known to be stereospecific for a D-α-methyl-substituted diketide substrate (dkD). MD simulations of two ternary complexes comprised of the enzyme, NADPH, and either the correct substrate, dkD, or its enantiomer (dkL) were performed. The coordinates for the A1/NADPH binary complex were obtained from a crystal structure (PDB entry 3MJS), and substrates were modeled in the binding pocket in conformations appropriate for reduction. Simulations were intended to reproduce the initial weak binding of the polyketide substrate to the enzyme. Long (tens of nanoseconds) MD simulations show that the correct substrate is retained in a conformation closer to the reactive configuration. Many short (up to a nanosecond) MD runs starting from the initial structures display evidence that Q364, three residues N-terminal to the catalytic tyrosine, forms a hydrogen bond to the incorrect dkL substrate to yield an unreactive conformation that is more favorable than the reactive configuration. This interaction is not as strong for dkD, as the D-α-methyl substituent is positioned between the glutamine and the reactive site. This result correlates with experimental findings [Zheng, J., et al. (2010) Structure 18, 913-922] in which a Q364H mutant was observed to lose stereospecificity.
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Affiliation(s)
- Mauro L Mugnai
- †Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Yue Shi
- ‡Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Adrian T Keatinge-Clay
- †Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.,§Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ron Elber
- †Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.,∥Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, United States
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34
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35
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Li Y, Fiers WD, Bernard S, Smith JL, Aldrich CC, Fecik RA. Polyketide intermediate mimics as probes for revealing cryptic stereochemistry of ketoreductase domains. ACS Chem Biol 2014; 9:2914-22. [PMID: 25299319 PMCID: PMC4273979 DOI: 10.1021/cb5006883] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 10/09/2014] [Indexed: 12/27/2022]
Abstract
Among natural product families, polyketides have shown the most promise for combinatorial biosynthesis of natural product-like libraries. Though recent research in the area has provided many mechanistic revelations, a basic-level understanding of kinetic and substrate tolerability is still needed before the full potential of combinatorial biosynthesis can be realized. We have developed a novel set of chemical probes for the study of ketoreductase domains of polyketide synthases. This chemical tool-based approach was validated using the ketoreductase of pikromycin module 2 (PikKR2) as a model system. Triketide substrate mimics 12 and 13 were designed to increase stability (incorporating a nonhydrolyzable thioether linkage) and minimize nonessential functionality (truncating the phosphopantetheinyl arm). PikKR2 reduction product identities as well as steady-state kinetic parameters were determined by a combination of LC-MS/MS analysis of synthetic standards and a NADPH consumption assay. The d-hydroxyl product is consistent with bioinformatic analysis and results from a complementary biochemical and molecular biological approach. When compared to widely employed substrates in previous studies, diketide 63 and trans-decalone 64, substrates 12 and 13 showed 2-10 fold lower K(M) values (2.4 ± 0.8 and 7.8 ± 2.7 mM, respectively), indicating molecular recognition of intermediate-like substrates. Due to an abundance of the nonreducable enol-tautomer, the k(cat) values were attenuated by as much as 15-336 fold relative to known substrates. This study reveals the high stereoselectivity of PikKR2 in the face of gross substrate permutation, highlighting the utility of a chemical probe-based approach in the study of polyketide ketoreductases.
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Affiliation(s)
- Yang Li
- Department
of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - William D. Fiers
- Department
of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Steffen
M. Bernard
- Chemical Biology Program, Department of Biological
Chemistry,
and Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Janet L. Smith
- Chemical Biology Program, Department of Biological
Chemistry,
and Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Courtney C. Aldrich
- Department
of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Robert A. Fecik
- Department
of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
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36
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Abstract
Natural products are important sources of pharmaceuticals, in part owing to their diverse biological activities. Enzymes from natural product biosynthetic pathways have become attractive candidates as biocatalysts for modifying the structures and bioactivities of these complex compounds. Numerous enzymes have been harvested to generate innovative scaffolds, large-scale synthesis of chiral building blocks, and semisynthesis of medicinally relevant natural product derivatives. This review discusses recent examples from three areas: (a) polyketide catalytic domain engineering geared toward synthesis of new polyketides, (b) engineering of tailoring enzymes (other than oxidative enzymes) as biocatalysts, and (c) in vitro total synthesis of natural products using purified enzyme components. With the availability of exponentially increasing genomic information and new genome mining tools, many new and powerful biocatalysts tailored for pharmaceutical synthesis will likely emerge from secondary metabolism.
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37
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Piasecki SK, Zheng J, Axelrod AJ, Detelich M, Keatinge-Clay AT. Structural and functional studies of a trans-acyltransferase polyketide assembly line enzyme that catalyzes stereoselective α- and β-ketoreduction. Proteins 2014; 82:2067-77. [PMID: 24634061 PMCID: PMC4142079 DOI: 10.1002/prot.24561] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 02/19/2014] [Accepted: 03/06/2014] [Indexed: 11/06/2022]
Abstract
While the cis-acyltransferase modular polyketide synthase assembly lines have largely been structurally dissected, enzymes from within the recently discovered trans-acyltransferase polyketide synthase assembly lines are just starting to be observed crystallographically. Here we examine the ketoreductase (KR) from the first polyketide synthase module of the bacillaene nonribosomal peptide synthetase/polyketide synthase at 2.35-Å resolution. This KR naturally reduces both α- and β-keto groups and is the only KR known to do so during the biosynthesis of a polyketide. The isolated KR not only reduced an N-acetylcysteamine-bound β-keto substrate to a D-β-hydroxy product, but also an N-acetylcysteamine-bound α-keto substrate to an L-α-hydroxy product. That the substrates must enter the active site from opposite directions to generate these stereochemistries suggests that the acyl-phosphopantetheine moiety is capable of accessing very different conformations despite being anchored to a serine residue of a docked acyl carrier protein. The features enabling stereocontrolled α-ketoreduction may not be extensive since a KR that naturally reduces a β-keto group within a cis-acyltransferase polyketide synthase was identified that performs a completely stereoselective reduction of the same α-keto substrate to generate the D-α-hydroxy product. A sequence analysis of trans-acyltransferase KRs reveals that a single residue, rather than a three-residue motif found in cis-acyltransferase KRs, is predictive of the orientation of the resulting β-hydroxyl group.
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Affiliation(s)
- Shawn K. Piasecki
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
| | - Jianting Zheng
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
| | - Abram J. Axelrod
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
| | - Madeline Detelich
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
| | - Adrian T. Keatinge-Clay
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
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38
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Hashimoto M, Koen T, Takahashi H, Suda C, Kitamoto K, Fujii I. Aspergillus oryzae CsyB catalyzes the condensation of two β-ketoacyl-CoAs to form 3-acetyl-4-hydroxy-6-alkyl-α-pyrone. J Biol Chem 2014; 289:19976-84. [PMID: 24895122 DOI: 10.1074/jbc.m114.569095] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The type III polyketide synthases from fungi produce a variety of secondary metabolites including pyrones, resorcinols, and resorcylic acids. We previously reported that CsyB from Aspergillus oryzae forms α-pyrone csypyrone B compounds when expressed in A. oryzae. Feeding experiments of labeled acetates indicated that a fatty acyl starter is involved in the reaction catalyzed by CsyB. Here we report the in vivo and in vitro reconstitution analysis of CsyB. When CsyB was expressed in Escherichia coli, we observed the production of 3-acetyl-4-hydroxy-α-pyrones with saturated or unsaturated straight aliphatic chains of C9-C17 in length at the 6 position. Subsequent in vitro analysis using recombinant CsyB revealed that CsyB could accept butyryl-CoA as a starter substrate and malonyl-CoA and acetoacetyl-CoA as extender substrates to form 3-acetyl-4-hydroxy-6-propyl-α-pyrone. CsyB also afforded dehydroacetic acid from two molecules of acetoacetyl-CoA. Furthermore, synthetic N-acetylcysteamine thioester of β-ketohexanoic acid was converted to 3-butanoyl-4-hydroxy-6-propyl-α-pyrone by CsyB. These results therefore confirmed that CsyB catalyzed the synthesis of β-ketoacyl-CoA from the reaction of the starter fatty acyl CoA thioesters with malonyl-CoA as the extender through decarboxylative condensation and further coupling with acetoacetyl-CoA to form 3-acetyl-4-hydroxy-6-alkyl-α-pyrone. CsyB is the first type III polyketide synthase that synthesizes 3-acetyl-4-hydroxy-6-alkyl-α-pyrone by catalyzed the coupling of two β-ketoacyl-CoAs.
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Affiliation(s)
- Makoto Hashimoto
- From the School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan and
| | - Tsukasa Koen
- From the School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan and
| | - Hiroaki Takahashi
- From the School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan and
| | - Chihiro Suda
- From the School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan and
| | - Katsuhiko Kitamoto
- the Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Isao Fujii
- From the School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan and
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Wan W, Tharp JM, Liu WR. Pyrrolysyl-tRNA synthetase: an ordinary enzyme but an outstanding genetic code expansion tool. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1059-70. [PMID: 24631543 DOI: 10.1016/j.bbapap.2014.03.002] [Citation(s) in RCA: 284] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 03/01/2014] [Accepted: 03/05/2014] [Indexed: 11/16/2022]
Abstract
The genetic incorporation of the 22nd proteinogenic amino acid, pyrrolysine (Pyl) at amber codon is achieved by the action of pyrrolysyl-tRNA synthetase (PylRS) together with its cognate tRNA(Pyl). Unlike most aminoacyl-tRNA synthetases, PylRS displays high substrate side chain promiscuity, low selectivity toward its substrate α-amine, and low selectivity toward the anticodon of tRNA(Pyl). These unique but ordinary features of PylRS as an aminoacyl-tRNA synthetase allow the Pyl incorporation machinery to be easily engineered for the genetic incorporation of more than 100 non-canonical amino acids (NCAAs) or α-hydroxy acids into proteins at amber codon and the reassignment of other codons such as ochre UAA, opal UGA, and four-base AGGA codons to code NCAAs.
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Affiliation(s)
- Wei Wan
- Department of Chemistry, Texas A&M University, College Station, TX 77845, USA
| | - Jeffery M Tharp
- Department of Chemistry, Texas A&M University, College Station, TX 77845, USA
| | - Wenshe R Liu
- Department of Chemistry, Texas A&M University, College Station, TX 77845, USA.
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40
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Liu WR. Reports from the Chemical Biology of Texas Symposium at the 69th Southwest Regional Meeting of the American Chemical Society. ACS Chem Biol 2014; 9:319-22. [PMID: 24556200 DOI: 10.1021/cb500046f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Wenshe R Liu
- Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States
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41
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Koryakina I, McArthur JB, Draelos MM, Williams GJ. Promiscuity of a modular polyketide synthase towards natural and non-natural extender units. Org Biomol Chem 2014; 11:4449-58. [PMID: 23681002 DOI: 10.1039/c3ob40633d] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Combinatorial biosynthesis approaches that involve modular type I polyketide synthases (PKSs) are proven strategies for the synthesis of polyketides. In general however, such strategies are usually limited in scope and utility due to the restricted substrate specificity of polyketide biosynthetic machinery. Herein, a panel of chemo-enzymatically synthesized acyl-CoA's was used to probe the promiscuity of a polyketide synthase. Promiscuity determinants were dissected, revealing that the KS is remarkably tolerant to a diverse array of extender units, while the AT likely discriminates between extender units that are native to the producing organism. Our data provides a clear blueprint for future enzyme engineering efforts, and sets the stage for harnessing extender unit promiscuity by employing various in vivo polyketide diversification strategies.
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Affiliation(s)
- Irina Koryakina
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
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42
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Kandziora N, Andexer JN, Moss SJ, Wilkinson B, Leadlay PF, Hahn F. Uncovering the origin of Z-configured double bonds in polyketides: intermediate E-double bond formation during borrelidin biosynthesis. Chem Sci 2014. [DOI: 10.1039/c4sc00883a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The dehydratase domain BorDH3 is assayed with a synthetic surrogate of the predicted tetraketide substrate and shown to be E-selective. Detailed NMR spectroscopic analysis of pre-borrelidin assigns the timing of the E-5 Z-isomerization to the very final steps of borrelidin biosynthesis.
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Affiliation(s)
- Nadine Kandziora
- Institut für Organische Chemie
- Leibniz Universität Hannover
- 30167 Hannover, Germany
| | - Jennifer N. Andexer
- Department of Biochemistry
- University of Cambridge (UK)
- Cambridge CB2 1QW, UK
- Institut für Pharmazeutische Wissenschaften
- Albert-Ludwigs-Universität Freiburg
| | - Steven J. Moss
- Isomerase Therapeutics
- Chesterford Research Park
- Cambridge CB10 1XL, UK
| | - Barrie Wilkinson
- Department of Molecular Microbiology
- John Innes Centre Norwich NR4 7UH
- UK
| | - Peter F. Leadlay
- Department of Biochemistry
- University of Cambridge (UK)
- Cambridge CB2 1QW, UK
| | - Frank Hahn
- Institut für Organische Chemie
- Leibniz Universität Hannover
- 30167 Hannover, Germany
- Department of Biochemistry
- University of Cambridge (UK)
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43
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Gay D, You YO, Keatinge-Clay A, Cane DE. Structure and stereospecificity of the dehydratase domain from the terminal module of the rifamycin polyketide synthase. Biochemistry 2013; 52:8916-28. [PMID: 24274103 DOI: 10.1021/bi400988t] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RifDH10, the dehydratase domain from the terminal module of the rifamycin polyketide synthase, catalyzes the stereospecific syn dehydration of the model substrate (2S,3S)-2-methyl-3-hydroxypentanoyl-RifACP10, resulting in the exclusive formation of (E)-2-methyl-2-pentenoyl-RifACP10. RifDH10 does not dehydrate any of the other three diastereomeric, RifACP10-bound, diketide thioester substrates. On the other hand, when EryACP6, from the sixth module of the erythromycin polyketide synthase, is substituted for RifACP10, RifDH10 stereospecifically dehydrates only (2R,3R)-2-methyl-3-hydroxypentanoyl-EryACP6 to give exclusively (E)-2-methyl-2-pentenoyl-EryACP6, with no detectable dehydration of any of the other three diastereomeric, EryACP6-bound, diketides. An identical alteration in substrate diastereospecificity was observed for the corresponding N-acetylcysteamine or pantetheine thioester analogues, regardless of acyl chain length or substitution pattern. Incubation of (2RS)-2-methyl-3-ketopentanoyl-RifACP10 with the didomain reductase-dehydratase RifKR10-RifDH10 yielded (E)-2-methyl-2-pentenoyl-RifACP10, the expected product of syn dehydration of (2S,3S)-2-methyl-3-hydroxypentanoyl-RifACP10, while incubation with the corresponding EryACP6-bound substrate, (2RS)-2-methyl-3-ketopentanoyl-EryACP6, gave only the reduction product (2S,3S)-2-methyl-3-hydroxypentanoyl-EryACP6 with no detectable dehydration. These results establish the intrinsic syn dehydration stereochemistry and substrate diastereoselectivity of RifDH10 and highlight the critical role of the natural RifACP10 domain in chaperoning the proper recognition and processing of the natural ACP-bound undecaketide substrate. The 1.82 Å resolution structure of RifDH10 reveals the atomic-resolution details of the active site and allows modeling of the syn dehydration of the (2S,3S)-2-methyl-3-hydroxyacyl-RifACP10 substrate. These results suggest that generation of the characteristic cis double bond of the rifamycins occurs after formation of the full-length RifACP10-bound acyclic trans-unsaturated undecaketide intermediate, most likely during the subsequent macrolactamization catalyzed by the amide synthase RifF.
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Affiliation(s)
- Darren Gay
- Department of Chemistry and Biochemistry, The University of Texas at Austin , 1 University Station A5300, Austin, Texas 78712-0165, United States
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44
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Hughes AJ, Tibby MR, Wagner DT, Brantley JN, Keatinge-Clay AT. Investigating the reactivities of a polyketide synthase module through fluorescent click chemistry. Chem Commun (Camb) 2013; 50:5276-8. [PMID: 24196586 DOI: 10.1039/c3cc47513a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A method for monitoring in vitro polyketide synthesis has been developed whereby nonchromophoric polyketide products are made brightly fluorescent in a simple, rapid, inexpensive, and bioorthogonal manner through CuAAC with a sulforhodamine B azide derivative.
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Affiliation(s)
- Amanda Jane Hughes
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX, USA.
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45
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Garg A, Khosla C, Cane DE. Coupled methyl group epimerization and reduction by polyketide synthase ketoreductase domains. Ketoreductase-catalyzed equilibrium isotope exchange. J Am Chem Soc 2013; 135:16324-7. [PMID: 24161343 DOI: 10.1021/ja408944s] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Incubation of [2-(2)H]-(2S,3R)-2-methyl-3-hydroxypentanoyl-SACP ([2-(2)H]-1a) with the epimerizing ketoreductase domain EryKR1 in the presence of a catalytic amount NADP(+) (0.05 equiv) resulted in time- and cofactor-dependent washout of deuterium from 1a, as a result of equilibrium isotope exchange of transiently generated [2-(2)H]-2-methyl-3-ketopentanoyl-ACP. Incubations of [2-(2)H]-(2S,3S)-2-methyl-3-hydroxy-pentanoyl-SACP with RifKR7 and with NysKR1 also resulted in time-dependent loss of deuterium. By contrast, incubations of [2-(2)H]-(2R,3S)-2-methyl-3-hydroxypentanoyl-SACP and [2-(2)H]-(2R,3R)-2-methyl-3-hydroxypentanoyl-SACP with the non-epimerizing ketoreductase domains EryKR6 and TylKR1, respectively, did not result in any significant washout of deuterium. The isotope exchange assay directly establishes that specific polyketide synthase ketoreductase domains also have an intrinsic epimerase activity, thus enabling mechanistic analysis of a key determinant of polyketide stereocomplexity.
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Affiliation(s)
- Ashish Garg
- Department of Chemistry, Brown University , Providence, Rhode Island 02912-9108, United States
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46
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Zheng J, Piasecki SK, Keatinge-Clay AT. Structural studies of an A2-type modular polyketide synthase ketoreductase reveal features controlling α-substituent stereochemistry. ACS Chem Biol 2013; 8:1964-71. [PMID: 23755878 PMCID: PMC4434595 DOI: 10.1021/cb400161g] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Modular polyketide synthase ketoreductases often set two stereocenters when reducing intermediates in the biosynthesis of a complex polyketide. Here we report the 2.55-Å resolution structure of an A2-type ketoreductase from the 11th module of the amphotericin polyketide synthase that sets a combination of l-α-methyl and l-β-hydroxyl stereochemistries and represents the final catalytically competent ketoreductase type to be structurally elucidated. Through structure-guided mutagenesis a double mutant of an A1-type ketoreductase was generated that functions as an A2-type ketoreductase on a diketide substrate analogue, setting an α-alkyl substituent in an l-orientation rather than in the d-orientation set by the unmutated ketoreductase. When the activity of the double mutant was examined in the context of an engineered triketide lactone synthase, the anticipated triketide lactone was not produced even though the ketoreductase-containing module still reduced the diketide substrate analogue as expected. These findings suggest that re-engineered ketoreductases may be catalytically outcompeted within engineered polyketide synthase assembly lines.
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Affiliation(s)
- Jianting Zheng
- Department of Chemistry & Biochemistry, University of Texas at Austin, Austin, TX 78712, USA
| | - Shawn K. Piasecki
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Adrian T. Keatinge-Clay
- Department of Chemistry & Biochemistry, University of Texas at Austin, Austin, TX 78712, USA,Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA,Corresponding Author:
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47
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You YO, Khosla C, Cane DE. Stereochemistry of reductions catalyzed by methyl-epimerizing ketoreductase domains of polyketide synthases. J Am Chem Soc 2013; 135:7406-9. [PMID: 23659177 PMCID: PMC3699853 DOI: 10.1021/ja4014776] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ketoreductase (KR) domains from modular polyketide synthases (PKSs) catalyze the reduction of 2-methyl-3-ketoacyl acyl carrier protein (ACP) substrates and in certain cases epimerization of the 2-methyl group as well. The structural and mechanistic basis of epimerization is poorly understood, and only a small number of such KRs been studied. In this work, we studied three recombinant KR domains with putative epimerase activity: NysKR1 from module 1 of the nystatin PKS, whose stereospecificity can be predicted from both the protein sequence and the product structure; RifKR7 from module 7 of the rifamycin PKS, whose stereospecificity cannot be predicted from the protein sequence; and RifKR10 from module 10 of the rifamycin PKS, whose specificity is unclear from both the sequence and the structure. Each KR was individually incubated with NADPH and (2R)- or (2RS)-2-methyl-3-ketopentanoyl-ACP generated enzymatically in situ or via chemoenzymatic synthesis, respectively. Chiral GC-MS analysis revealed that each KR stereospecifically produced the corresponding (2S,3S)-2-methyl-3-hydroxypentanoyl-ACP in which the 2-methyl substituent had undergone KR-catalyzed epimerization. Thus, our results have led to the identification of a prototypical set of KR domains that generate (2S,3S)-2-methyl-3-hydroxyacyl products in the course of polyketide biosynthesis.
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Affiliation(s)
- Young-Ok You
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
| | - Chaitan Khosla
- Departments of Chemical Engineering, Chemistry, and Biochemistry, Stanford University, Stanford, California 94305
| | - David E. Cane
- Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108
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Häckh M, Müller M, Lüdeke S. Substrate-Dependent Stereospecificity of Tyl-KR1: An Isolated Polyketide Synthase Ketoreductase Domain fromStreptomyces fradiae. Chemistry 2013; 19:8922-8. [DOI: 10.1002/chem.201300554] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Indexed: 11/11/2022]
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49
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Zou Y, Yin H, Kong D, Deng Z, Lin S. ATrans-Acting Ketoreductase in Biosynthesis of a Symmetric Polyketide Dimer SIA7248. Chembiochem 2013; 14:679-83. [DOI: 10.1002/cbic.201300068] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Indexed: 11/07/2022]
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50
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Zheng J, Keatinge-Clay AT. The status of type I polyketide synthase ketoreductases. MEDCHEMCOMM 2013. [DOI: 10.1039/c2md20191g] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The functional dissection of type I polyketide synthases has established that ketoreductases most commonly set the orientations of the hydroxyl and alkyl substituents of complex polyketides. Here we review the biochemical, structural biology, and engineering studies that have helped elucidate how stereocontrol is enforced by these enzymes.
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Affiliation(s)
- Jianting Zheng
- Department of Chemistry and Biochemistry
- The University of Texas at Austin
- USA
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