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Expanding the Enzyme Repertoire for Sugar Nucleotide Epimerization: The CDP-Tyvelose 2-Epimerase from Thermodesulfatator atlanticus for Glucose/Mannose Interconversion. Appl Environ Microbiol 2021; 87:AEM.02131-20. [PMID: 33277270 PMCID: PMC7851689 DOI: 10.1128/aem.02131-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Epimerization of sugar nucleotides is central to the structural diversification of monosaccharide building blocks for cellular biosynthesis. Epimerase applicability to carbohydrate synthesis can be limited, however, by the high degree of substrate specificity exhibited by most sugar nucleotide epimerases. Here, we discovered a promiscuous type of CDP-tyvelose 2-epimerase (TyvE)-like enzyme that promotes C2-epimerization in all nucleotide (CDP, UDP, GDP, ADP, TDP)-activated forms of d-glucose. This new epimerase, originating from Thermodesulfatator atlanticus, is a functional homodimer that contains one tightly bound NAD+/subunit and shows optimum activity at 70°C and pH 9.5. The enzyme exhibits a k cat with CDP-dglucose of ∼1.0 min-1 (pH 7.5, 60°C). To characterize the epimerase kinetically and probe its substrate specificity, we developed chemo-enzymatic syntheses for CDP-dmannose, CDP-6-deoxy-dglucose, CDP-3-deoxy-dglucose and CDP-6-deoxy-dxylo-hexopyranos-4-ulose. Attempts to obtain CDP-dparatose and CDP-dtyvelose were not successful. Using high-resolution carbohydrate analytics and in situ NMR to monitor the enzymatic conversions (60°C, pH 7.5), we show that the CDP-dmannose/CDP-dglucose ratio at equilibrium is 0.67 (± 0.1), determined from the kinetic Haldane relationship and directly from the reaction. We further show that deoxygenation at sugar C6 enhances the enzyme activity 5-fold compared to CDP-dglucose whereas deoxygenation at C3 renders the substrate inactive. Phylogenetic analysis places the T. atlanticus epimerase into a distinct subgroup within the sugar nucleotide epimerase family of SDR (short-chain dehydrogenases/reductases), for which the current study now provides the functional context. Collectively, our results expand an emerging toolbox of epimerase-catalyzed reactions for sugar nucleotide synthesis.IMPORTANCE Epimerases of the sugar nucleotide-modifying class of enzymes have attracted considerable interest in carbohydrate (bio)chemistry, for the mechanistic challenges and the opportunities for synthesis involved in the reactions catalyzed. Discovery of new epimerases with expanded scope of sugar nucleotide substrates used is important to promote the mechanistic inquiry and can facilitate the development of new enzyme applications. Here, a CDP-tyvelose 2-epimerase-like enzyme from Thermodesulfatator atlanticus is shown to catalyze sugar C2 epimerization in CDP-glucose and other nucleotide-activated forms of dglucose. The reactions are new to nature in the context of enzymatic sugar nucleotide modification. The current study explores the substrate scope of the discovered C2-epimerase and, based on modeling, suggests structure-function relationships that may be important for specificity and catalysis.
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Bury PDS, Huang F, Li S, Sun Y, Leadlay PF, Dias MVB. Structural Basis of the Selectivity of GenN, an Aminoglycoside N-Methyltransferase Involved in Gentamicin Biosynthesis. ACS Chem Biol 2017; 12:2779-2787. [PMID: 28876898 DOI: 10.1021/acschembio.7b00466] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gentamicins are heavily methylated, clinically valuable pseudotrisaccharide antibiotics produced by Micromonospora echinospora. GenN has been characterized as an S-adenosyl-l-methionine-dependent methyltransferase with low sequence similarity to other enzymes. It is responsible for the 3″-N-methylation of 3″-dehydro-3″-amino-gentamicin A2, an essential modification of ring III in the biosynthetic pathway to the gentamicin C complex. Purified recombinant GenN also efficiently catalyzes 3″-N-methylation of related aminoglycosides kanamycin B and tobramycin, which both contain an additional hydroxymethyl group at the C5″ position in ring III. We have obtained eight cocrystal structures of GenN, at a resolution of 2.2 Å or better, including the binary complex of GenN and S-adenosyl-l-homocysteine (SAH) and the ternary complexes of GenN, SAH, and several aminoglycosides. The GenN structure reveals several features not observed in any other N-methyltransferase that fit it for its role in gentamicin biosynthesis. These include a novel N-terminal domain that might be involved in protein:protein interaction with upstream enzymes of the gentamicin X2 biosynthesis and two long loops that are involved in aminoglycoside substrate recognition. In addition, the analysis of structures of GenN in complex with different ligands, supported by the results of active site mutagenesis, has allowed us to propose a catalytic mechanism and has revealed the structural basis for the surprising ability of native GenN to act on these alternative substrates.
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Affiliation(s)
- Priscila dos Santos Bury
- Department
of Microbiology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Fanglu Huang
- Department
of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, United Kingdom
| | - Sicong Li
- Key
Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry
of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Yuhui Sun
- Key
Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry
of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan, People’s Republic of China
| | - Peter F. Leadlay
- Department
of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, United Kingdom
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Lv M, Ji X, Zhao J, Li Y, Zhang C, Su L, Ding W, Deng Z, Yu Y, Zhang Q. Characterization of a C3 Deoxygenation Pathway Reveals a Key Branch Point in Aminoglycoside Biosynthesis. J Am Chem Soc 2016; 138:6427-35. [PMID: 27120352 DOI: 10.1021/jacs.6b02221] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Apramycin is a clinically interesting aminoglycoside antibiotic (AGA) containing a highly unique bicyclic octose moiety, and this octose is deoxygenated at the C3 position. Although the biosynthetic pathways for most 2-deoxystreptamine-containing AGAs have been well characterized, the pathway for apramycin biosynthesis, including the C3 deoxygenation process, has long remained unknown. Here we report detailed investigation of apramycin biosynthesis by a series of genetic, biochemical and bioinformatical studies. We show that AprD4 is a novel radical S-adenosyl-l-methionine (SAM) enzyme, which uses a noncanonical CX3CX3C motif for binding of a [4Fe-4S] cluster and catalyzes the dehydration of paromamine, a pseudodisaccharide intermediate in apramycin biosynthesis. We also show that AprD3 is an NADPH-dependent reductase that catalyzes the reduction of the dehydrated product from AprD4-catalyzed reaction to generate lividamine, a C3' deoxygenated product of paromamine. AprD4 and AprD3 do not form a tight catalytic complex, as shown by protein complex immunoprecipitation and other assays. The AprD4/AprD3 enzyme system acts on different pseudodisaccharide substrates but does not catalyze the deoxygenation of oxyapramycin, an apramycin analogue containing a C3 hydroxyl group on the octose moiety, suggesting that oxyapramycin and apramycin are partitioned into two parallel pathways at an early biosynthetic stage. Functional dissection of the C6 dehydrogenase AprQ shows the crosstalk between different AGA biosynthetic gene clusters from the apramycin producer Streptomyces tenebrarius, and reveals the remarkable catalytic versatility of AprQ. Our study highlights the intriguing chemistry in apramycin biosynthesis and nature's ingenuity in combinatorial biosynthesis of natural products.
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Affiliation(s)
- Meinan Lv
- Key Laboratory of Combinatory Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University , Wuhan, 430071, China
| | - Xinjian Ji
- Department of Chemistry, Fudan University , Shanghai, 200433, China
| | - Junfeng Zhao
- Key Laboratory of Combinatory Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University , Wuhan, 430071, China.,Department of Chemistry, Fudan University , Shanghai, 200433, China
| | - Yongzhen Li
- Department of Chemistry, Fudan University , Shanghai, 200433, China
| | - Chen Zhang
- Department of Chemistry, Fudan University , Shanghai, 200433, China
| | - Li Su
- Key Laboratory of Combinatory Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University , Wuhan, 430071, China
| | - Wei Ding
- Department of Chemistry, Fudan University , Shanghai, 200433, China
| | - Zixin Deng
- Key Laboratory of Combinatory Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University , Wuhan, 430071, China
| | - Yi Yu
- Key Laboratory of Combinatory Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Wuhan University , Wuhan, 430071, China
| | - Qi Zhang
- Department of Chemistry, Fudan University , Shanghai, 200433, China
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Itoh Y, Bröcker MJ, Sekine SI, Söll D, Yokoyama S. Dimer-dimer interaction of the bacterial selenocysteine synthase SelA promotes functional active-site formation and catalytic specificity. J Mol Biol 2014; 426:1723-35. [PMID: 24456689 DOI: 10.1016/j.jmb.2014.01.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/09/2014] [Accepted: 01/12/2014] [Indexed: 10/25/2022]
Abstract
The 21st amino acid, selenocysteine (Sec), is incorporated translationally into proteins and is synthesized on its specific tRNA (tRNA(Sec)). In Bacteria, the selenocysteine synthase SelA converts Ser-tRNA(Sec), formed by seryl-tRNA synthetase, to Sec-tRNA(Sec). SelA, a member of the fold-type-I pyridoxal 5'-phosphate-dependent enzyme superfamily, has an exceptional homodecameric quaternary structure with a molecular mass of about 500kDa. Our previously determined crystal structures of Aquifex aeolicus SelA complexed with tRNA(Sec) revealed that the ring-shaped decamer is composed of pentamerized SelA dimers, with two SelA dimers arranged to collaboratively interact with one Ser-tRNA(Sec). The SelA catalytic site is close to the dimer-dimer interface, but the significance of the dimer pentamerization in the catalytic site formation remained elusive. In the present study, we examined the quaternary interactions and demonstrated their importance for SelA activity by systematic mutagenesis. Furthermore, we determined the crystal structures of "depentamerized" SelA variants with mutations at the dimer-dimer interface that prevent pentamerization. These dimeric SelA variants formed a distorted and inactivated catalytic site and confirmed that the pentamer interactions are essential for productive catalytic site formation. Intriguingly, the conformation of the non-functional active site of dimeric SelA shares structural features with other fold-type-I pyridoxal 5'-phosphate-dependent enzymes with native dimer or tetramer (dimer-of-dimers) quaternary structures.
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Affiliation(s)
- Yuzuru Itoh
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan; Laboratory of Membrane and Cytoskeleton Dynamics, Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Markus J Bröcker
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Shun-ichi Sekine
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan; Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA; Department of Chemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Shigeyuki Yokoyama
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan; RIKEN Structural Biology Laboratory, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
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Romo AJ, Liu HW. Mechanisms and structures of vitamin B(6)-dependent enzymes involved in deoxy sugar biosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1814:1534-47. [PMID: 21315852 PMCID: PMC3115481 DOI: 10.1016/j.bbapap.2011.02.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 01/08/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
Abstract
PLP is well-regarded for its role as a coenzyme in a number of diverse enzymatic reactions. Transamination, deoxygenation, and aldol reactions mediated by PLP-dependent enzymes enliven and enrich deoxy sugar biosynthesis, endowing these compounds with unique structures and contributing to their roles as determinants of biological activity in many natural products. The importance of deoxy aminosugars in natural product biosynthesis has spurred several recent structural investigations of sugar aminotransferases. The structure of a PMP-dependent enzyme catalyzing the C-3 deoxygenation reaction in the biosynthesis of ascarylose was also determined. These studies, and the crystal structures they have provided, offer a wealth of new insights regarding the enzymology of PLP/PMP-dependent enzymes in deoxy sugar biosynthesis. In this review, we consider these recent achievements in the structural biology of deoxy sugar biosynthetic enzymes and the important implications they hold for understanding enzyme catalysis and natural product biosynthesis in general. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology.
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Affiliation(s)
- Anthony J. Romo
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
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Thibodeaux C, Melançon C, Liu HW. Biosynthese von Naturstoffzuckern und enzymatische Glycodiversifizierung. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801204] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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7
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Smith P, Szu PH, Bui C, Liu HW, Tsai SC. Structure and mutagenic conversion of E1 dehydrase: at the crossroads of dehydration, amino transfer, and epimerization. Biochemistry 2008; 47:6329-41. [PMID: 18491919 DOI: 10.1021/bi702449p] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP) are highly versatile coenzymes whose importance is well recognized. The capability of PLP/PMP-dependent enzymes to catalyze a diverse array of chemical reactions is attributed to fine-tuning of the cofactor-substrate interactions in the active site. CDP-6-deoxy-L-threo-D-glycero-4-hexulose 3-dehydrase (E1), along with its reductase (E3), catalyzes the C-3 deoxygenation of CDP-4-keto-6-deoxy-D-glucose to form the dehydrated product, CDP-4-keto-3,6-dideoxy- d-glucose, in the ascarylose biosynthetic pathway. This product is the progenitor to most 3,6-dideoxyhexoses, which are the major antigenic determinants of many Gram-negative pathogens. The dimeric [2Fe-2S] protein, E 1, cloned from Yersinia pseudotuberculosis, is the only known enzyme whose catalysis involves the direct participation of PMP in one-electron redox chemistry. E1 also contains an unusual [2Fe-2S] cluster with a previously unknown binding motif (C-X 57-C-X 1-C-X 7-C). Herein we report the first X-ray crystal structure of E1, which exhibits an aspartate aminotransferase (AAT) fold. A comparison of the E1 active site architecture with homologous structures uncovers residues critical for the dehydration versus transamination activity. Site-directed mutagenesis of four E1 residues, D194H, Y217H, H220K, and F345H, converted E 1 from a PMP-dependent dehydrase to a PLP/glutamate-dependent aminotransferase. The E1 quadruple mutant, having been conferred this altered enzyme activity, can transaminate the natural substrate to CDP-4,6-dideoxy-4-amino-D-galactose without E3. Taken together, these results provide the molecular basis of the functional switch of E1 toward dehydration, epimerization, and transamination. The insights gained from these studies can be used for the development of inhibitors of disease-relevant PLP/PMP-dependent enzymes.
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Affiliation(s)
- Peter Smith
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697, USA
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Thibodeaux CJ, Melançon CE, Liu HW. Natural-product sugar biosynthesis and enzymatic glycodiversification. Angew Chem Int Ed Engl 2008; 47:9814-59. [PMID: 19058170 PMCID: PMC2796923 DOI: 10.1002/anie.200801204] [Citation(s) in RCA: 320] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Many biologically active small-molecule natural products produced by microorganisms derive their activities from sugar substituents. Changing the structures of these sugars can have a profound impact on the biological properties of the parent compounds. This realization has inspired attempts to derivatize the sugar moieties of these natural products through exploitation of the sugar biosynthetic machinery. This approach requires an understanding of the biosynthetic pathway of each target sugar and detailed mechanistic knowledge of the key enzymes. Scientists have begun to unravel the biosynthetic logic behind the assembly of many glycosylated natural products and have found that a core set of enzyme activities is mixed and matched to synthesize the diverse sugar structures observed in nature. Remarkably, many of these sugar biosynthetic enzymes and glycosyltransferases also exhibit relaxed substrate specificity. The promiscuity of these enzymes has prompted efforts to modify the sugar structures and alter the glycosylation patterns of natural products through metabolic pathway engineering and enzymatic glycodiversification. In applied biomedical research, these studies will enable the development of new glycosylation tools and generate novel glycoforms of secondary metabolites with useful biological activity.
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Affiliation(s)
- Christopher J. Thibodeaux
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX. (USA), 78712
| | - Charles E. Melançon
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX. (USA), 78712
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX. (USA), 78712
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9
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Hong L, Zhao Z, Liu HW. Characterization of SpnQ from the spinosyn biosynthetic pathway of Saccharopolyspora spinosa: mechanistic and evolutionary implications for C-3 deoxygenation in deoxysugar biosynthesis. J Am Chem Soc 2007; 128:14262-3. [PMID: 17076492 PMCID: PMC2515268 DOI: 10.1021/ja0649670] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The C-3 deoxygenation step in the biosynthesis of d-forosamine (4-N,N-dimethylamino-2,3,4,6-tetradeoxy-d-threo-hexopyranose), a constituent of spinosyn produced by Saccharopolyspora spinosa, was investigated. The spnQ gene, proposed to encode a TDP-4-keto-2,6-dideoxy-d-glucose 3-dehydratase was cloned and overexpressed in E. coli. Characterization of the purified enzyme established that it is a PMP and iron-sulfur containing enzyme which catalyzes the C-3 deoxygenation in a reductase-dependent manner similar to that of the previously well characterized hexose 3-dehydrase E1 from Yersinia pseudotuberculosis. However, unlike E1, which has evolved to work with a specific reductase partner present in its gene cluster, SpnQ lacks a specific reductase, and works efficiently with general cellular reductases ferredoxin/ferredoxin reductase or flavodoxin/flavodoxin reductase. SpnQ also catalyzes C-4 transamination in the absence of an electron transfer intermediary and in the presence of PLP and l-glutamate. Under the same conditions, both E1 and the related hexose 3-dehydrase, ColD, catalyze C-3 deoxygenation. Thus, SpnQ possesses important features which distinguish it from other well studied homologues, suggesting unique evolutionary pathways for each of the three hexose 3-dehydrases studied thus far.
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Affiliation(s)
- Lin Hong
- Division of Medicinal Chemistry, College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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Mansoorabadi SO, Thibodeaux CJ, Liu HW. The diverse roles of flavin coenzymes--nature's most versatile thespians. J Org Chem 2007; 72:6329-42. [PMID: 17580897 PMCID: PMC2519020 DOI: 10.1021/jo0703092] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Flavin coenzymes play a variety of roles in biological systems. This Perspective highlights the chemical versatility of flavins by reviewing research on five flavoenzymes that have been studied in our laboratory. Each of the enzymes discussed in this review [the acyl-CoA dehydrogenases (ACDs), CDP-6-deoxy-l-threo-d-glycero-4-hexulose-3-dehydrase reductase (E3), CDP-4-aceto-3,6-dideoxygalactose synthase (YerE), UDP-galactopyranose mutase (UGM), and type II isopentenyl diphosphate:dimethylallyl diphosphate isomerase (IDI-2)] utilizes flavin in a distinct role. In particular, the catalytic mechanisms of two of these enzymes, UGM and IDI-2, may involve novel flavin chemistry.
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Affiliation(s)
- Steven O. Mansoorabadi
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712, USA
| | - Christopher J. Thibodeaux
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712, USA
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712, USA
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Melançon CE, Hong L, White JA, Liu YN, Liu HW. Characterization of TDP-4-keto-6-deoxy-D-glucose-3,4-ketoisomerase from the D-mycaminose biosynthetic pathway of Streptomyces fradiae: in vitro activity and substrate specificity studies. Biochemistry 2007; 46:577-90. [PMID: 17209568 PMCID: PMC2515277 DOI: 10.1021/bi061907y] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Deoxysugars are critical structural elements for the bioactivity of many natural products. Ongoing work on elucidating a variety of deoxysugar biosynthetic pathways has paved the way for manipulation of these pathways for the generation of structurally diverse glycosylated natural products. In the course of this work, the biosynthesis of d-mycaminose in the tylosin pathway of Streptomyces fradiae was investigated. Attempts to reconstitute the entire mycaminose biosynthetic machinery in a heterologous host led to the discovery of a previously overlooked gene, tyl1a, encoding an enzyme thought to convert TDP-4-keto-6-deoxy-d-glucose to TDP-3-keto-6-deoxy-d-glucose, a 3,4-ketoisomerization reaction in the pathway. Tyl1a has now been overexpressed, purified, and assayed, and its activity has been verified by product analysis. Incubation of Tyl1a and the C-3 aminotransferase TylB, the next enzyme in the pathway, produced TDP-3-amino-3,6-dideoxy-d-glucose, confirming that these two enzymes act sequentially. Steady state kinetic parameters of the Tyl1a-catalyzed reaction were determined, and the ability of Tyl1a and TylB to process a C-2 deoxygenated substrate and a CDP-linked substrate was also demonstrated. Enzymes catalyzing 3,4-ketoisomerization of hexoses represent a new class of enzymes involved in unusual sugar biosynthesis. The fact that Tyl1a exhibits a relaxed substrate specificity holds potential for future deoxysugar biosynthetic engineering endeavors.
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Affiliation(s)
- Charles E. Melançon
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Lin Hong
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Jessica A. White
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
| | - Yung-nan Liu
- Division of Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712
- To whom correspondence and reprint requests should be addressed. Phone: 512-232-7811, Fax: 512-471-2746. E-mail:
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Ikeno S, Aoki D, Hamada M, Hori M, Tsuchiya KS. DNA sequencing and transcriptional analysis of the kasugamycin biosynthetic gene cluster from Streptomyces kasugaensis M338-M1. J Antibiot (Tokyo) 2006; 59:18-28. [PMID: 16568715 DOI: 10.1038/ja.2006.4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Streptomyces kasugaensis M338-M1 produces the aminoglycoside antibiotic kasugamycin (KSM). We previously cloned, sequenced and characterized the KSM acetyltransferase, transporter, and some of the biosynthetic genes from this strain. To identify other potential genes in a chromosome walk experiment, a 6.8-kb EcoRI-PstI region immediately downstream from the KSM transporter genes was sequenced. Five open reading frames (designated as kasN, kasO, kasP, kasQ, kasR) and the 5' region of kasA were found in this region. The genes are apparently co-transcribed as bicistrons, all of which are co-directional except for the kasPQ transcript. Homology analysis of the deduced products of kasN, kasP, kasQ and kasR revealed similarities with known enzymes: KasN, D-amino acid oxidase from Pseudomonas aeruginosa (35% identity); KasP, F420-dependent H4MPT reductase from Streptomyces lavendulae (33% identity); KasQ, UDP-N-acetylglucosamine 2-epimerase from Streptomyces verticillus (45% identity); and KasR, NDP-hexose 3,4-dehydratase from Streptomyces cyanogenus (38% identity); respectively. A gel retardation assay showed that KasT, a putative pathway-specific regulator for this gene cluster, bound to the upstream region of kasN and to the intergenic region of kasQ-kasR, suggesting that the expression of these operons is under the control of the regulator protein.
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Affiliation(s)
- Souichi Ikeno
- Showa Pharmaceutical University, 3-3165 Higashi Tamagawagakuen, Machida-shi, Tokyo 194-8543, Japan.
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Smith P, Lin A, Szu PH, Liu HW, Tsai SC. Biosynthesis of a 3,6-dideoxyhexose: crystallization and X-ray diffraction of CDP-6-deoxy-L-threo-D-glycero-4-hexulose-3-dehydrase (E1) for ascarylose biosynthesis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:231-4. [PMID: 16511309 PMCID: PMC2197195 DOI: 10.1107/s1744309106003721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 01/30/2006] [Indexed: 11/10/2022]
Abstract
CDP-6-deoxy-L-threo-D-glycero-4-hexulose-3-dehydrase (E1), along with its reductase (E3), catalyzes the unusual C-3 deoxygenation of CDP-6-deoxy-L-threo-D-glycero-4-hexulose to form CDP-3,6-dideoxy-L-threo-D-glycero-4-hexulose in CDP-ascarylose biosynthesis [Chen et al. (1996), Biochemistry, 35, 16412-16420]. This dimeric [2Fe-2S] protein, cloned from the bacteria Yersinia pseudotuberculosis, is currently the only known example of an enzyme that uses a vitamin B6-derived pyridoxamine 5'-phosphate (PMP) cofactor to carry out one-electron chemistry [Agnihotri & Liu (2001), Bioorg. Chem. 29, 234-257]. It also exhibits a [2Fe-2S] cluster-binding motif (C-X57-C-X1-C-X7-C) which has not been observed previously [Agnihotri et al. (2004), Biochemistry, 43, 14265-14274] The recombinant 97.7 kDa dimer was crystallized in the trigonal space group P3(2), with unit-cell parameters a = b = 97.37, c = 142.2 A, alpha = beta = 90, gamma = 120 degrees. A data set has been collected to 1.9 A resolution. A full MAD data set was also collected at the iron absorption edge that diffracted to 2.0 A.
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Affiliation(s)
- Peter Smith
- Department of Molecular Biology and Biochemistry, Department of Chemistry, University of California, Irvine, CA 92697, USA
| | - Ava Lin
- Department of Molecular Biology and Biochemistry, Department of Chemistry, University of California, Irvine, CA 92697, USA
| | - Ping-hui Szu
- Division of Medicinal Chemistry, College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA
| | - Shiou-Chuan Tsai
- Department of Molecular Biology and Biochemistry, Department of Chemistry, University of California, Irvine, CA 92697, USA
- Correspondence e-mail:
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14
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Pongdee R, Liu HW. Elucidation of enzyme mechanisms using fluorinated substrate analogues. Bioorg Chem 2004; 32:393-437. [PMID: 15381404 DOI: 10.1016/j.bioorg.2004.06.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Indexed: 11/24/2022]
Abstract
A great variety of biological reactions that are physiologically important are catalyzed by enzymes. Understanding the reaction course of these enzyme-catalyzed transformations are of significant importance since the insights gained from these experiments may facilitate the design of methods to control or mimic their actions. A common strategy to study enzyme catalyses is to use fluorinated substrate analogues as mechanistic probes, since fluorine is an effective hydroxyl group mimic and can also be used to replace a hydrogen atom. Using fluorinated substrate probes have enabled researchers to obtain crucial information regarding the catalytic mechanism of enzymatic reactions. Many of these compounds are good enzyme inhibitors and have been developed into clinically useful chemotherapeutic agents. This review will discuss some examples of the use of fluorine containing compounds as mechanistic probes/enzyme inhibitors, many of which are selected from our own work.
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Affiliation(s)
- Rongson Pongdee
- Division of Medicinal Chemistry, Department of Chemistry and Biochemistry, College of Pharmacy, University of Texas, Austin, TX 78712, USA
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15
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Abstract
Carbohydrates are highly abundant biomolecules found extensively in nature. Besides playing important roles in energy storage and supply, they often serve as essential biosynthetic precursors or structural elements needed to sustain all forms of life. A number of unusual sugars that have certain hydroxyl groups replaced by a hydrogen, an amino group, or an alkyl side chain play crucial roles in determining the biological activity of the parent natural products in bacterial lipopolysaccharides or secondary metabolite antibiotics. Recent investigation of the biosynthesis of these monosaccharides has led to the identification of the gene clusters whose protein products facilitate the unusual sugar formation from the ubiquitous NDP-glucose precursors. This review summarizes the mechanistic studies of a few enzymes crucial to the biosynthesis of C-2, C-3, C-4, and C-6 deoxysugars, the characterization and mutagenesis of nucleotidyl transferases that can recognize and couple structural analogs of their natural substrates and the identification of glycosyltransferases with promiscuous substrate specificity. Information gleaned from these studies has allowed pathway engineering, resulting in the creation of new macrolides with unnatural deoxysugar moieties for biological activity screening. This represents a significant progress toward our goal of searching for more potent agents against infectious diseases and malignant tumors.
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Affiliation(s)
- Xuemei M He
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA.
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16
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Metzler DE, Metzler CM, Sauke DJ. Some Pathways of Carbohydrate Metabolism. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50023-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Abstract
In the past few years, there have been many important advances in our understanding of the biosynthesis of deoxysugars. Mechanistic studies have shed light on how enzymes can cleave C-O bonds, epimerize the configuration of substituents and reduce keto groups to make deoxysugars. Exciting progress has also been made in our comprehension of the genetics of deoxysugar biosynthesis in antibiotics. All this information is important for potential medical and biotechnological applications, such as drug discovery based on combinatorial biology.
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Affiliation(s)
- D A Johnson
- Department of Chemistry, University of Minnesota, Minneapolis 55455, USA
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