1
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Wang Y, Das S, Aboulhosn K, Champagne SE, Gemmel PM, Skinner KC, Ragsdale SW, Zimmerman PM, Narayan ARH. Nature-Inspired Radical Pyridoxal-Mediated C-C Bond Formation. J Am Chem Soc 2024; 146:23321-23329. [PMID: 39106078 DOI: 10.1021/jacs.4c05997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/07/2024]
Abstract
Pyridoxal-5'-phosphate (PLP) and derivatives of this cofactor enable a plethora of reactions in both enzyme-mediated and free-in-solution transformations. With few exceptions in each category, such chemistry has predominantly involved two-electron processes. This sometimes poses a significant challenge for using PLP to build tetrasubstituted carbon centers, especially when the reaction is reversible. The ability to access radical pathways is paramount to broadening the scope of reactions catalyzed by this coenzyme. In this study, we demonstrate the ability to access a radical PLP-based intermediate and engage this radical intermediate in a number of C-C bond-forming reactions. By selection of an appropriate oxidant, single-electron oxidation of the quinonoid intermediate can be achieved, which can subsequently be applied to C-C bond-forming reactions. Through this radical reaction pathway, we synthesized a series of α-tertiary amino acids and esters to investigate the substrate scope and identify nonproductive reaction pathways. Beyond the amino acid model system, we demonstrate that other classes of amine substrates can be applied in this reaction and that a range of small molecule reagents can serve as coupling partners to the semiquinone radical. We anticipate that this versatile semiquinone radical species will be central to the development of a range of novel reactions.
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Affiliation(s)
- Ye Wang
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Soumik Das
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kareem Aboulhosn
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Sarah E Champagne
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Philipp M Gemmel
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kevin C Skinner
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Paul M Zimmerman
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alison R H Narayan
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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2
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Daniel-Ivad P, Ryan KS. New reactions by pyridoxal phosphate-dependent enzymes. Curr Opin Chem Biol 2024; 81:102472. [PMID: 38815536 DOI: 10.1016/j.cbpa.2024.102472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 05/02/2024] [Accepted: 05/08/2024] [Indexed: 06/01/2024]
Abstract
Pyridoxal phosphate (PLP) is a cofactor that is widely employed in enzymology. This pyridine-containing cofactor can be used for reactions ranging from transaminations to oxidations. The catalytic versatility can be understood by considering the chemical features of this cofactor. In recent years, exciting new reactions involving PLP have been discovered in natural products biosynthesis, upending our understanding of what this cofactor is capable of. Here we review some of the most exciting PLP-dependent reactions from the last five years.
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Affiliation(s)
- Phillip Daniel-Ivad
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Katherine S Ryan
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada.
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3
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Vuksanovic N, Melkonian TR, Serrano DA, Schwabacher AW, Silvaggi NR. Structural and Biochemical Characterization of MppQ, an L-Enduracididine Biosynthetic Enzyme from Streptomyces hygroscopicus. Biochemistry 2023; 62:3105-3115. [PMID: 37890134 DOI: 10.1021/acs.biochem.3c00428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2023]
Abstract
MppQ is an enzyme of unknown function from Streptomyces hygroscopicus (ShMppQ) that operates in the biosynthesis of the nonproteinogenic amino acid L-enduracididine (L-End). Since L-End is a component of several peptides showing activity against antibiotic-resistant pathogens, understanding its biosynthetic pathway could facilitate the development of chemoenzymatic routes to novel antibiotics. Herein, we report on the crystal structures of ShMppQ complexed with pyridoxal-5'-phosphate (PLP) and pyridoxamine-5'-phosphate (PMP). ShMppQ is similar to fold-type I PLP-dependent aminotransferases like aspartate aminotransferase. The tertiary structure of ShMppQ is composed of an N-terminal extension, a large domain, and a small domain. The active site is placed at the junction of the large and small domains and includes residues from both protomers of the homodimer. We also report the first functional characterization of MppQ, which we incubated with the enzymatically produced 2-ketoenduracidine and observed the conversion to L-End, establishing ShMppQ as the final enzyme in L-End biosynthesis. Additionally, we have observed that MppQ has a relatively high affinity for 2-keto-5-guanidinovaleric acid (i.e., 2-ketoarginine), a shunt product of MppP, indicating the potential role of MppQ in increasing the efficiency of L-End biosynthesis by converting 2-ketoarginine back to the starting material, l-arginine. A panel of potential amino-donor substrates was tested for the transamination activity against a saturating concentration of 2-ketoarginine in end-point assays. Most l-Arg was produced with l-ornithine as the donor substrate. Steady-state kinetic analysis of the transamination reaction with l-Orn and 2-ketoarginine shows that the kinetic constants are in line with those for the amino donor substrate of other fold-type I aminotransferases.
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Affiliation(s)
- Nemanja Vuksanovic
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Trevor R Melkonian
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Division of Chemical Biology and Medicinal Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Dante A Serrano
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
- Department of Chemistry, Pennsylvania State University, 302 Chemistry Building, University Park, Pennsylvania 16802, United States
| | - Alan W Schwabacher
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
| | - Nicholas R Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 North Cramer Street, Milwaukee, Wisconsin 53211, United States
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4
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Daniel-Ivad PG, Van Lanen S, Ryan KS. Structure of the Oxygen, Pyridoxal Phosphate-Dependent Capuramycin Biosynthetic Protein Cap15. Biochemistry 2023; 62:2611-2621. [PMID: 37556254 DOI: 10.1021/acs.biochem.3c00216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Pyridoxal phosphate-dependent enzymes able to use oxygen as a co-substrate have emerged in multiple protein families. Here, we use crystallography to solve the 2.40 Å resolution crystal structure of Cap15, a nucleoside biosynthetic enzyme that catalyzes the oxidative decarboxylation of glycyl uridine. Our structural study captures the internal aldimine, pinpointing the active site lysine as K230 and showing the site of phosphate binding. Our docking studies reveal how Cap15 is able to catalyze a stereoselective deprotonation reaction, and bioinformatic analysis reveals active site residues that distinguish Cap15 from the structurally related d-glucosaminate-6-phosphate ammonia lyase and l-seryl-tRNA(Sec) selenium transferase (SelA). Our work provides the structural basis for further mechanistic investigation of a unique biosynthetic enzyme and provides a blueprint for understanding how oxygen reactivity emerged in the SelA-like protein family.
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Affiliation(s)
- Phillip G Daniel-Ivad
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Steven Van Lanen
- Pharmaceutical Sciences Department, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Katherine S Ryan
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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5
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Cordoza J, Chen PYT, Blaustein LR, Lima ST, Fiore MF, Chekan JR, Moore BS, McKinnie SMK. Mechanistic and Structural Insights into a Divergent PLP-Dependent l-Enduracididine Cyclase from a Toxic Cyanobacterium. ACS Catal 2023; 13:9817-9828. [PMID: 37497377 PMCID: PMC10367076 DOI: 10.1021/acscatal.3c01294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 06/21/2023] [Indexed: 07/28/2023]
Abstract
Cyclic arginine noncanonical amino acids (ncAAs) are found in several actinobacterial peptide natural products with therapeutically useful antibacterial properties. The preparation of ncAAs like enduracididine and capreomycidine currently takes multiple biosynthetic or chemosynthetic steps, thus limiting the commercial availability and applicability of these cyclic guanidine-containing amino acids. We recently discovered and characterized the biosynthetic pathway of guanitoxin, a potent freshwater cyanobacterial neurotoxin, that contains an arginine-derived cyclic guanidine phosphate within its highly polar structure. The ncAA l-enduracididine is an early intermediate in guanitoxin biosynthesis and is produced by GntC, a unique pyridoxal-5'-phosphate (PLP)-dependent enzyme. GntC catalyzes a cyclodehydration from a stereoselectively γ-hydroxylated l-arginine precursor via a reaction that functionally and mechanistically diverges from previously established actinobacterial cyclic arginine ncAA pathways. Herein, we interrogate l-enduracididine biosynthesis from the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using spectroscopy, stable isotope labeling techniques, and X-ray crystallography structure-guided site-directed mutagenesis. GntC initially facilitates the reversible deprotonations of the α- and β-positions of its substrate before catalyzing an irreversible diastereoselective dehydration and subsequent intramolecular cyclization. The comparison of holo- and substrate-bound GntC structures and activity assays on site-specific mutants further identified amino acid residues that contribute to the overall catalytic mechanism. These interdisciplinary efforts at structurally and functionally characterizing GntC enable an improved understanding of how nature divergently produces cyclic arginine ncAAs and generate additional tools for their biocatalytic production and downstream biological applications.
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Affiliation(s)
- Jennifer
L. Cordoza
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
| | - Percival Yang-Ting Chen
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
| | - Linnea R. Blaustein
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
| | - Stella T. Lima
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
- Center
for Nuclear Energy in Agriculture, University
of São Paulo, Piracicaba, São Paulo 13416-000, Brazil
| | - Marli F. Fiore
- Center
for Nuclear Energy in Agriculture, University
of São Paulo, Piracicaba, São Paulo 13416-000, Brazil
| | - Jonathan R. Chekan
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
- Department
of Chemistry and Biochemistry, University
of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
| | - Bradley S. Moore
- Department
of Chemistry and Biochemistry, University
of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92903, United States
| | - Shaun M. K. McKinnie
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
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6
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Melkonian TR, Vuksanovic N, Silvaggi NR. Probing mechanistic questions in the PLP- and O 2-dependent l-Arg oxidases. Methods Enzymol 2023; 685:493-529. [PMID: 37245913 DOI: 10.1016/bs.mie.2023.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The pyridoxal-5'-phosphate-dependent l-Arg oxidases are unusual in that they are able to catalyze 4-electron oxidations of arginine using only the PLP cofactor. No metals or other accessory cosubstrates are involved; only arginine, dioxygen, and PLP. The catalytic cycles of these enzymes are replete with colored intermediates whose accumulation and decay can be monitored spectrophotometrically. This makes the l-Arg oxidases excellent subjects for detailed mechanistic investigations. They are worth studying, because they can teach us much about how PLP-dependent enzymes modulate the cofactor (structure-function-dynamics) and how new activities can arise from existing enzyme scaffolds. Herein we describe a series of experiments that can be used to probe the mechanisms of l-Arg oxidases. These methods by no means originated in our lab but were learned from talented researchers in other enzyme fields (flavoenzymes and Fe(II)-dependent oxygenases) and have been adapted to fit the requirements of our system. We present practical information for expressing and purifying the l-Arg oxidases, protocols for running stopped-flow experiments to examine the reactions with l-Arg and with dioxygen, and a tandem mass spectrometry-based quench-flow assay to follow the accumulation of the products of the hydroxylating l-Arg oxidases.
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Affiliation(s)
- Trevor R Melkonian
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | | | - Nicholas R Silvaggi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, United States.
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7
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Cordoza JL, Chen PYT, Blaustein LR, Lima ST, Fiore MF, Chekan JR, Moore BS, McKinnie SMK. Mechanistic and structural insights into a divergent PLP-dependent L-enduracididine cyclase from a toxic cyanobacterium. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.21.533663. [PMID: 36993528 PMCID: PMC10055224 DOI: 10.1101/2023.03.21.533663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Cyclic arginine noncanonical amino acids (ncAAs) are found in several actinobacterial peptide natural products with therapeutically useful antibacterial properties. The preparation of ncAAs like enduracididine and capreomycidine currently takes multiple biosynthetic or chemosynthetic steps, thus limiting the commercial availability and applicability of these cyclic guanidine-containing amino acids. We recently discovered and characterized the biosynthetic pathway of guanitoxin, a potent freshwater cya-nobacterial neurotoxin, that contains an arginine-derived cyclic guanidine phosphate within its highly polar structure. The ncAA L-enduracididine is an early intermediate in guanitoxin biosynthesis and is produced by GntC, a unique pyridoxal-5'-phosphate (PLP)-dependent enzyme. GntC catalyzes a cyclodehydration from a stereoselectively γ-hydroxylated L-arginine precursor via a reaction that functionally and mechanistically diverges from previously established actinobacterial cyclic arginine ncAA pathways. Herein, we interrogate L-enduracididine biosynthesis from the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using spectroscopic, stable isotope labeling techniques, and X-ray crystal structure-guided site-directed mutagenesis. GntC initially facilitates the reversible deprotonations of the α- and β-positions of its substrate prior to catalyzing an irreversible diastereoselective dehydration and subsequent intramolecular cyclization. The comparison of holo- and substrate bound GntC structures and activity assays on sitespecific mutants further identified amino acid residues that contribute to the overall catalytic mechanism. These interdisciplinary efforts at structurally and functionally characterizing GntC enables an improved understanding of how Nature divergently produces cyclic arginine ncAAs and generates additional tools for their biocatalytic production and downstream biological applications.
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8
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Lima ST, Fallon TR, Cordoza JL, Chekan JR, Delbaje E, Hopiavuori AR, Alvarenga DO, Wood SM, Luhavaya H, Baumgartner JT, Dörr FA, Etchegaray A, Pinto E, McKinnie SMK, Fiore MF, Moore BS. Biosynthesis of Guanitoxin Enables Global Environmental Detection in Freshwater Cyanobacteria. J Am Chem Soc 2022; 144:9372-9379. [PMID: 35583956 PMCID: PMC9247102 DOI: 10.1021/jacs.2c01424] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Harmful cyanobacterial blooms (cyanoHABs) cause recurrent toxic events in global watersheds. Although public health agencies monitor the causal toxins of most cyanoHABs and scientists in the field continue developing precise detection and prediction tools, the potent anticholinesterase neurotoxin, guanitoxin, is not presently environmentally monitored. This is largely due to its incompatibility with widely employed analytical methods and instability in the environment, despite guanitoxin being among the most lethal cyanotoxins. Here, we describe the guanitoxin biosynthesis gene cluster and its rigorously characterized nine-step metabolic pathway from l-arginine in the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024. Through environmental sequencing data sets, guanitoxin (gnt) biosynthetic genes are repeatedly detected and expressed in municipal freshwater bodies that have undergone past toxic events. Knowledge of the genetic basis of guanitoxin biosynthesis now allows for environmental, biosynthetic gene monitoring to establish the global scope of this neurotoxic organophosphate.
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Affiliation(s)
- Stella T Lima
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, Sao Paulo 13416-000, Brazil
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
| | - Timothy R Fallon
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
| | - Jennifer L Cordoza
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Jonathan R Chekan
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
| | - Endrews Delbaje
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, Sao Paulo 13416-000, Brazil
| | - Austin R Hopiavuori
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Danillo O Alvarenga
- Department of Biology, University of Copenhagen, Copenhagen, DK 2100, Denmark
| | - Steffaney M Wood
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
| | - Hanna Luhavaya
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
| | - Jackson T Baumgartner
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Felipe A Dörr
- School of Pharmaceutical Sciences, University of São Paulo, São Paulo, Ribeirao Preto, Sao Paulo 05508-000, Brazil
| | - Augusto Etchegaray
- Center for Life Sciences, Graduate Program in Health Sciences, Pontifical Catholic University of Campinas (PUC-Campinas), Campinas, Sao Paulo 13087-571, Brazil
| | - Ernani Pinto
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, Sao Paulo 13416-000, Brazil
| | - Shaun M K McKinnie
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Marli F Fiore
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, Sao Paulo 13416-000, Brazil
| | - Bradley S Moore
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093, United States
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9
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A shared mechanistic pathway for pyridoxal phosphate-dependent arginine oxidases. Proc Natl Acad Sci U S A 2021; 118:2012591118. [PMID: 34580201 DOI: 10.1073/pnas.2012591118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2021] [Indexed: 01/02/2023] Open
Abstract
The mechanism by which molecular oxygen is activated by the organic cofactor pyridoxal phosphate (PLP) for oxidation reactions remains poorly understood. Recent work has identified arginine oxidases that catalyze desaturation or hydroxylation reactions. Here, we investigate a desaturase from the Pseudoalteromonas luteoviolacea indolmycin pathway. Our work, combining X-ray crystallographic, biochemical, spectroscopic, and computational studies, supports a shared mechanism with arginine hydroxylases, involving two rounds of single-electron transfer to oxygen and superoxide rebound at the 4' carbon of the PLP cofactor. The precise positioning of a water molecule in the active site is proposed to control the final reaction outcome. This proposed mechanism provides a unified framework to understand how oxygen can be activated by PLP-dependent enzymes for oxidation of arginine and elucidates a shared mechanistic pathway and intertwined evolutionary history for arginine desaturases and hydroxylases.
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10
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McErlean M, Liu X, Cui Z, Gust B, Van Lanen SG. Identification and characterization of enzymes involved in the biosynthesis of pyrimidine nucleoside antibiotics. Nat Prod Rep 2021; 38:1362-1407. [PMID: 33404015 DOI: 10.1039/d0np00064g] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Covering: up to September 2020 Hundreds of nucleoside-based natural products have been isolated from various microorganisms, several of which have been utilized in agriculture as pesticides and herbicides, in medicine as therapeutics for cancer and infectious disease, and as molecular probes to study biological processes. Natural products consisting of structural modifications of each of the canonical nucleosides have been discovered, ranging from simple modifications such as single-step alkylations or acylations to highly elaborate modifications that dramatically alter the nucleoside scaffold and require multiple enzyme-catalyzed reactions. A vast amount of genomic information has been uncovered the past two decades, which has subsequently allowed the first opportunity to interrogate the chemically intriguing enzymatic transformations for the latter type of modifications. This review highlights (i) the discovery and potential applications of structurally complex pyrimidine nucleoside antibiotics for which genetic information is known, (ii) the established reactions that convert the canonical pyrimidine into a new nucleoside scaffold, and (iii) the important tailoring reactions that impart further structural complexity to these molecules.
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Affiliation(s)
- M McErlean
- Department of Pharmaceutical Science, College of Pharmacy, University of Kentucky, USA.
| | - X Liu
- Department of Pharmaceutical Science, College of Pharmacy, University of Kentucky, USA.
| | - Z Cui
- Department of Pharmaceutical Science, College of Pharmacy, University of Kentucky, USA.
| | - B Gust
- Pharmaceutical Institute, Department of Pharmaceutical Biology, University of Tübingen, Germany
| | - S G Van Lanen
- Department of Pharmaceutical Science, College of Pharmacy, University of Kentucky, USA.
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11
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Oxygen reactivity with pyridoxal 5'-phosphate enzymes: biochemical implications and functional relevance. Amino Acids 2020; 52:1089-1105. [PMID: 32844248 PMCID: PMC7497351 DOI: 10.1007/s00726-020-02885-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 08/18/2020] [Indexed: 12/29/2022]
Abstract
The versatility of reactions catalyzed by pyridoxal 5'-phosphate (PLP) enzymes is largely due to the chemistry of their extraordinary catalyst. PLP is necessary for many reactions involving amino acids. Reaction specificity is controlled by the orientation of the external aldimine intermediate that is formed upon addition of the amino acidic substrate to the coenzyme. The breakage of a specific bond of the external aldimine gives rise to a carbanionic intermediate. From this point, the different reaction pathways diverge leading to multiple activities: transamination, decarboxylation, racemization, elimination, and synthesis. A significant novelty appeared approximately 30 years ago when it was reported that some PLP-dependent decarboxylases are able to consume molecular oxygen transforming an amino acid into a carbonyl compound. These side paracatalytic reactions could be particularly relevant for human health, also considering that some of these enzymes are responsible for the synthesis of important neurotransmitters such as γ-aminobutyric acid, dopamine, and serotonin, whose dysregulation under oxidative conditions could have important implications in neurodegenerative states. However, the reactivity of PLP enzymes with dioxygen is not confined to mammals/animals. In fact, some plant PLP decarboxylases have been reported to catalyze oxidative reactions producing carbonyl compounds. Moreover, other recent reports revealed the existence of new oxidase activities catalyzed by new PLP enzymes, MppP, RohP, Ind4, CcbF, PvdN, Cap15, and CuaB. These PLP enzymes belong to the bacterial and fungal kingdoms and are present in organisms synthesizing bioactive compounds. These new PLP activities are not paracatalytic and could only scratch the surface on a wider and unexpected catalytic capability of PLP enzymes.
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12
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Chen M, Liu CT, Tang Y. Discovery and Biocatalytic Application of a PLP-Dependent Amino Acid γ-Substitution Enzyme That Catalyzes C-C Bond Formation. J Am Chem Soc 2020; 142:10506-10515. [PMID: 32434326 DOI: 10.1021/jacs.0c03535] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pyridoxal phosphate (PLP)-dependent enzymes can catalyze transformations of l-amino acids at α, β, and γ positions. These enzymes are frequently involved in the biosynthesis of nonproteinogenic amino acids as building blocks of natural products and are attractive biocatalysts. Here, we report the discovery of a two-step enzymatic synthesis of (2S,6S)-6-methyl pipecolate 1, from the biosynthetic pathway of citrinadin. The key enzyme CndF is PLP-dependent and catalyzes the synthesis of (S)-2-amino-6-oxoheptanoate 3 that is in equilibrium with the cyclic Schiff base. The second enzyme CndE is a stereoselective imine reductase that gives 1. Biochemical characterization of CndF showed this enzyme performs γ-elimination of O-acetyl-l-homoserine to generate the vinylglycine ketimine, which is subjected to nucleophilic attack by acetoacetate to form the new Cγ-Cδ bond in 3 and complete the γ-substitution reaction. CndF displays promiscuity toward different β-keto carboxylate and esters. With use of an Aspergillus strain expressing CndF and CndE, feeding various alkyl-β-keto esters led to the biosynthesis of 6-substituted l-pipecolates. The discovery of CndF expands the repertoire of reactions that can be catalyzed by PLP-dependent enzymes.
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Affiliation(s)
- Mengbin Chen
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Chun-Ting Liu
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California 90095, United States.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yi Tang
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California 90095, United States.,Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, United States
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13
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Hoffarth ER, Rothchild KW, Ryan KS. Emergence of oxygen- and pyridoxal phosphate-dependent reactions. FEBS J 2020; 287:1403-1428. [PMID: 32142210 DOI: 10.1111/febs.15277] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 11/29/2019] [Accepted: 03/03/2020] [Indexed: 12/21/2022]
Abstract
Pyridoxal 5'-phosphate (PLP) is an organic cofactor employed by ~ 4% of enzymes. The structure of the PLP cofactor allows for the stabilization of carbanions through resonance. A small number of PLP-dependent enzymes employ molecular oxygen as a cosubstrate. Here, we review the biological roles and possible mechanisms of these enzymes, and we observe that these enzymes are found in multiple protein families, suggesting that reaction with oxygen might have emerged de novo in several protein families and thus could be directed to emerge again through laboratory evolution experiments.
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Affiliation(s)
- Elesha R Hoffarth
- Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
| | | | - Katherine S Ryan
- Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
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Pyridoxal-5'-phosphate-dependent bifunctional enzyme catalyzed biosynthesis of indolizidine alkaloids in fungi. Proc Natl Acad Sci U S A 2019; 117:1174-1180. [PMID: 31882449 DOI: 10.1073/pnas.1914777117] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Indolizidine alkaloids such as anticancer drugs vinblastine and vincristine are exceptionally attractive due to their widespread occurrence, prominent bioactivity, complex structure, and sophisticated involvement in the chemical defense for the producing organisms. However, the versatility of the indolizidine alkaloid biosynthesis remains incompletely addressed since the knowledge about such biosynthetic machineries is only limited to several representatives. Herein, we describe the biosynthetic gene cluster (BGC) for the biosynthesis of curvulamine, a skeletally unprecedented antibacterial indolizidine alkaloid from Curvularia sp. IFB-Z10. The molecular architecture of curvulamine results from the functional collaboration of a highly reducing polyketide synthase (CuaA), a pyridoxal-5'-phosphate (PLP)-dependent aminotransferase (CuaB), an NADPH-dependent dehydrogenase (CuaC), and a FAD-dependent monooxygenase (CuaD), with its transportation and abundance regulated by a major facilitator superfamily permease (CuaE) and a Zn(II)Cys6 transcription factor (CuaF), respectively. In contrast to expectations, CuaB is bifunctional and capable of catalyzing the Claisen condensation to form a new C-C bond and the α-hydroxylation of the alanine moiety in exposure to dioxygen. Inspired and guided by the distinct function of CuaB, our genome mining effort discovers bipolamines A-I (bipolamine G is more antibacterial than curvulamine), which represent a collection of previously undescribed polyketide alkaloids from a silent BGC in Bipolaris maydis ATCC48331. The work provides insight into nature's arsenal for the indolizidine-coined skeletal formation and adds evidence in support of the functional versatility of PLP-dependent enzymes in fungi.
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Abstract
Natural nonproteinogenic amino acids vastly outnumber the well-known 22 proteinogenic amino acids. Such amino acids are generated in specialized metabolic pathways. In these pathways, diverse biosynthetic transformations, ranging from isomerizations to the stereospecific functionalization of C-H bonds, are employed to generate structural diversity. The resulting nonproteinogenic amino acids can be integrated into more complex natural products. Here we review recently discovered biosynthetic routes to freestanding nonproteinogenic α-amino acids, with an emphasis on work reported between 2013 and mid-2019.
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Affiliation(s)
- Jason B Hedges
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Katherine S Ryan
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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16
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Hedges JB, Ryan KS. In vitro Reconstitution of the Biosynthetic Pathway to the Nitroimidazole Antibiotic Azomycin. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201903500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jason B. Hedges
- Department of Chemistry University of British Columbia Vancouver British Columbia Canada
| | - Katherine S. Ryan
- Department of Chemistry University of British Columbia Vancouver British Columbia Canada
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17
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Hedges JB, Ryan KS. In vitro Reconstitution of the Biosynthetic Pathway to the Nitroimidazole Antibiotic Azomycin. Angew Chem Int Ed Engl 2019; 58:11647-11651. [DOI: 10.1002/anie.201903500] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/23/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Jason B. Hedges
- Department of Chemistry University of British Columbia Vancouver British Columbia Canada
| | - Katherine S. Ryan
- Department of Chemistry University of British Columbia Vancouver British Columbia Canada
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18
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Asano Y, Yasukawa K. Identification and development of amino acid oxidases. Curr Opin Chem Biol 2019; 49:76-83. [DOI: 10.1016/j.cbpa.2018.10.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 10/16/2018] [Accepted: 10/22/2018] [Indexed: 12/23/2022]
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Du YL, Ryan KS. Pyridoxal phosphate-dependent reactions in the biosynthesis of natural products. Nat Prod Rep 2019; 36:430-457. [DOI: 10.1039/c8np00049b] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We review reactions catalyzed by pyridoxal phosphate-dependent enzymes, highlighting enzymes reported in the recent natural product biosynthetic literature.
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Affiliation(s)
- Yi-Ling Du
- Institute of Pharmaceutical Biotechnology
- Zhejiang University School of Medicine
- Hangzhou
- China
| | - Katherine S. Ryan
- Department of Chemistry
- University of British Columbia
- Vancouver
- Canada
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