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Vogel U, Da Costa M, Alvarez Quispe C, Stragier R, Joosten HJ, Beerens K, Desmet T. The Conversion of UDP-Glc to UDP-Man: In Silico and Biochemical Exploration To Improve the Catalytic Efficiency of CDP-Tyvelose C2-Epimerases. Chembiochem 2023; 24:e202300549. [PMID: 37728070 DOI: 10.1002/cbic.202300549] [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: 08/04/2023] [Revised: 09/14/2023] [Accepted: 09/18/2023] [Indexed: 09/21/2023]
Abstract
A promiscuous CDP-tyvelose 2-epimerase (TyvE) from Thermodesulfatator atlanticus (TaTyvE) belonging to the nucleotide sugar active short-chain dehydrogenase/reductase superfamily (NS-SDRs) was recently discovered. TaTyvE performs the slow conversion of NDP-glucose (NDP-Glc) to NDP-mannose (NDP-Man). Here, we present the sequence fingerprints that are indicative of the conversion of UDP-Glc to UDP-Man in TyvE-like enzymes based on the heptagonal box motifs. Our data-mining approach led to the identification of 11 additional TyvE-like enzymes for the conversion of UDP-Glc to UDP-Man. We characterized the top two wild-type candidates, which show a 15- and 20-fold improved catalytic efficiency, respectively, on UDP-Glc compared to TaTyvE. In addition, we present a quadruple variant of one of the identified enzymes with a 70-fold improved catalytic efficiency on UDP-Glc compared to TaTyvE. These findings could help the design of new nucleotide production pathways starting from a cheap sugar substrate like glucose or sucrose.
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Affiliation(s)
- Ulrike Vogel
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Matthieu Da Costa
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Carlos Alvarez Quispe
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Robin Stragier
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Henk-Jan Joosten
- Bio-Prodict BV, Nieuwe Marktstraat 54E, 6511 AA, Nijmegen, The Netherlands
| | - Koen Beerens
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
| | - Tom Desmet
- Centre for Synthetic Biology (CSB), Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium
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2
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Rapp C, Nidetzky B. Hydride Transfer Mechanism of Enzymatic Sugar Nucleotide C2 Epimerization Probed with a Loose-Fit CDP-Glucose Substrate. ACS Catal 2022; 12:6816-6830. [PMID: 35747200 PMCID: PMC9207888 DOI: 10.1021/acscatal.2c00257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 05/12/2022] [Indexed: 11/29/2022]
Abstract
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Transient oxidation–reduction
through hydride transfer with
tightly bound NAD coenzyme is used by a large class of sugar nucleotide
epimerases to promote configurational inversion of carbon stereocenters
in carbohydrate substrates. A requirement for the epimerases to coordinate
hydride abstraction and re-addition with substrate rotation in the
binding pocket poses a challenge for dynamical protein conformational
selection linked to enzyme catalysis. Here, we studied the thermophilic
C2 epimerase from Thermodesulfatator atlanticus (TaCPa2E) in combination with a slow CDP-glucose
substrate (kcat ≈ 1.0 min–1; 60 °C) to explore the sensitivity of the enzymatic hydride
transfer toward environmental fluctuations affected by temperature
(20–80 °C). We determined noncompetitive primary kinetic
isotope effects (KIE) due to 2H at the glucose C2 and showed
that a normal KIE on the kcat (Dkcat) reflects isotope sensitivity of
the hydrogen abstraction to enzyme-NAD+ in a rate-limiting
transient oxidation. The Dkcat peaked at 40 °C was 6.1 and decreased to 2.1 at low (20 °C)
and 3.3 at high temperature (80 °C). The temperature profiles
for kcat with the 1H and 2H substrate showed a decrease in the rate below a dynamically
important breakpoint (∼40 °C), suggesting an equilibrium
shift to an impaired conformational landscape relevant for catalysis
in the low-temperature region. Full Marcus-like model fits of the
rate and KIE profiles provided evidence for a high-temperature reaction
via low-frequency conformational sampling associated with a broad
distribution of hydride donor–acceptor distances (long-distance
population centered at 3.31 ± 0.02 Å), only poorly suitable
for quantum mechanical tunneling. Collectively, dynamical characteristics
of TaCPa2E-catalyzed hydride transfer during transient
oxidation of CDP-glucose reveal important analogies to mechanistically
simpler enzymes such as alcohol dehydrogenase and dihydrofolate reductase.
A loose-fit substrate (in TaCPa2E) resembles structural
variants of these enzymes by extensive dynamical sampling to balance
conformational flexibility and catalytic efficiency.
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Affiliation(s)
- Christian Rapp
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 10-12/1, 8010 Graz, Austria
| | - Bernd Nidetzky
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 10-12/1, 8010 Graz, Austria
- Austrian Centre of Industrial Biotechnology (ACIB), Petersgasse 14, 8010 Graz, Austria
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3
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Suh CE, Carder HM, Wendlandt AE. Selective Transformations of Carbohydrates Inspired by Radical-Based Enzymatic Mechanisms. ACS Chem Biol 2021; 16:1814-1828. [PMID: 33988380 DOI: 10.1021/acschembio.1c00190] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Enzymes are a longstanding source of inspiration for synthetic reaction development. However, enzymatic reactivity and selectivity are frequently untenable in a synthetic context, as the principles that govern control in an enzymatic setting often do not translate to small molecule catalysis. Recent synthetic methods have revealed the viability of using small molecule catalysts to promote highly selective radical-mediated transformations of minimally protected sugar substrates. These transformations share conceptual similarities with radical SAM enzymes found in microbial carbohydrate biosynthesis and present opportunities for synthetic chemists to access microbial and unnatural carbohydrate building blocks without the need for protecting groups or lengthy synthetic sequences. Here, we highlight strategies through which radical reaction pathways can enable the site-, regio-, and diastereoselective transformation of minimally protected carbohydrates in both synthetic and enzymatic systems.
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Affiliation(s)
- Carolyn E. Suh
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Hayden M. Carder
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alison E. Wendlandt
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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4
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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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5
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Borg AJE, Beerens K, Pfeiffer M, Desmet T, Nidetzky B. Stereo-electronic control of reaction selectivity in short-chain dehydrogenases: Decarboxylation, epimerization, and dehydration. Curr Opin Chem Biol 2020; 61:43-52. [PMID: 33166830 DOI: 10.1016/j.cbpa.2020.09.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 09/18/2020] [Accepted: 09/27/2020] [Indexed: 12/20/2022]
Abstract
Sugar nucleotide-modifying enzymes of the short-chain dehydrogenase/reductase type use transient oxidation-reduction by a tightly bound nicotinamide cofactor as a common strategy of catalysis to promote a diverse set of reactions, including decarboxylation, single- or double-site epimerization, and dehydration. Although the basic mechanistic principles have been worked out decades ago, the finely tuned control of reactivity and selectivity in several of these enzymes remains enigmatic. Recent evidence on uridine 5'-diphosphate (UDP)-glucuronic acid decarboxylases (UDP-xylose synthase, UDP-apiose/UDP-xylose synthase) and UDP-glucuronic acid-4-epimerase suggests that stereo-electronic constraints established at the enzyme's active site control the selectivity, and the timing of the catalytic reaction steps, in the conversion of the common substrate toward different products. The mechanistic idea of stereo-electronic control is extended to epimerases and dehydratases that deprotonate the Cα of the transient keto-hexose intermediate. The human guanosine 5'-diphosphate (GDP)-mannose 4,6-dehydratase was recently shown to use a minimal catalytic machinery, exactly as predicted earlier from theoretical considerations, for the β-elimination of water from the keto-hexose species.
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Affiliation(s)
- Annika J E Borg
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, 8010, Graz, Austria
| | - Koen Beerens
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, 9000, Ghent, Belgium
| | - Martin Pfeiffer
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, 8010, Graz, Austria; Austrian Centre of Industrial Biotechnology (acib), 8010, Graz, Austria
| | - Tom Desmet
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, 9000, Ghent, Belgium; Austrian Centre of Industrial Biotechnology (acib), 8010, Graz, Austria
| | - Bernd Nidetzky
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, 8010, Graz, Austria; Austrian Centre of Industrial Biotechnology (acib), 8010, Graz, Austria.
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6
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Van Overtveldt S, Da Costa M, Gevaert O, Joosten HJ, Beerens K, Desmet T. Determinants of the Nucleotide Specificity in the Carbohydrate Epimerase Family 1. Biotechnol J 2020; 15:e2000132. [PMID: 32761842 DOI: 10.1002/biot.202000132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/20/2020] [Indexed: 11/09/2022]
Abstract
In recent years, carbohydrate epimerases have attracted increasing attention as promising biocatalysts for the production of specialty sugars and derivatives. The vast majority of these enzymes are active on nucleotide-activated sugars, rather than on their free counterparts. Although such epimerases are known to have a clear preference for a particular nucleotide (UDP, GDP, CDP, or ADP), very little is known about the determinants of the respective specificities. In this work, sequence motifs are identified that correlate with the different nucleotide specificities in one of the main epimerase superfamilies, carbohydrate epimerase 1 (CEP1). To confirm their relevance, GDP- and CDP-specific residues are introduced into the UDP-glucose 4-epimerase from Thermus thermophilus, resulting in a 3-fold and 13-fold reduction in KM for GDP-Glc and CDP-Glc, respectively. Moreover, several variants are severely crippled in UDP-Glc activity, which further underlines the crucial role of the identified positions. Hence, the analysis should prove to be valuable for the further exploration and application of epimerases involved in carbohydrate synthesis.
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Affiliation(s)
- Stevie Van Overtveldt
- Centre for Synthetic Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Gent, 9000, Belgium
| | - Matthieu Da Costa
- Centre for Synthetic Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Gent, 9000, Belgium
| | - Ophelia Gevaert
- Centre for Synthetic Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Gent, 9000, Belgium
| | - Henk-Jan Joosten
- Bio-Prodict BV, Nieuwe Marktstraat 54E, Nijmegen, 6511 AA, The Netherlands
| | - Koen Beerens
- Centre for Synthetic Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Gent, 9000, Belgium
| | - Tom Desmet
- Centre for Synthetic Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Gent, 9000, Belgium
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7
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Borg AJE, Dennig A, Weber H, Nidetzky B. Mechanistic characterization of UDP-glucuronic acid 4-epimerase. FEBS J 2020; 288:1163-1178. [PMID: 32645249 PMCID: PMC7984243 DOI: 10.1111/febs.15478] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 06/22/2020] [Accepted: 07/06/2020] [Indexed: 12/27/2022]
Abstract
UDP-glucuronic acid (UDP-GlcA) is a central precursor in sugar nucleotide biosynthesis and common substrate for C4-epimerases and decarboxylases releasing UDP-galacturonic acid (UDP-GalA) and UDP-pentose products, respectively. Despite the different reactions catalyzed, the enzymes are believed to share mechanistic analogy rooted in their joint membership to the short-chain dehydrogenase/reductase (SDR) protein superfamily: Oxidation at the substrate C4 by enzyme-bound NAD+ initiates the catalytic pathway. Here, we present mechanistic characterization of the C4-epimerization of UDP-GlcA, which in comparison with the corresponding decarboxylation has been largely unexplored. The UDP-GlcA 4-epimerase from Bacillus cereus functions as a homodimer and contains one NAD+ /subunit (kcat = 0.25 ± 0.01 s-1 ). The epimerization of UDP-GlcA proceeds via hydride transfer from and to the substrate's C4 while retaining the enzyme-bound cofactor in its oxidized form (≥ 97%) at steady state and without trace of decarboxylation. The kcat for UDP-GlcA conversion shows a kinetic isotope effect of 2.0 (±0.1) derived from substrate deuteration at C4. The proposed enzymatic mechanism involves a transient UDP-4-keto-hexose-uronic acid intermediate whose formation is rate-limiting overall, and is governed by a conformational step before hydride abstraction from UDP-GlcA. Precise positioning of the substrate in a kinetically slow binding step may be important for the epimerase to establish stereo-electronic constraints in which decarboxylation of the labile β-keto acid species is prevented effectively. Mutagenesis and pH studies implicate the conserved Tyr149 as the catalytic base for substrate oxidation and show its involvement in the substrate positioning step. Collectively, this study suggests that based on overall mechanistic analogy, stereo-electronic control may be a distinguishing feature of catalysis by SDR-type epimerases and decarboxylases active on UDP-GlcA.
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Affiliation(s)
- Annika J E Borg
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Austria
| | - Alexander Dennig
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Austria.,Austrian Centre of Industrial Biotechnology, Graz, Austria
| | - Hansjörg Weber
- Institute of Organic Chemistry, Graz University of Technology, NAWI Graz, Austria
| | - Bernd Nidetzky
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Austria.,Austrian Centre of Industrial Biotechnology, Graz, Austria
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8
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Yan Y, Yang J, Wang L, Xu D, Yu Z, Guo X, Horsman GP, Lin S, Tao M, Huang SX. Biosynthetic access to the rare antiarose sugar via an unusual reductase-epimerase. Chem Sci 2020; 11:3959-3964. [PMID: 34122866 PMCID: PMC8152690 DOI: 10.1039/c9sc05766h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Rubrolones, isatropolones, and rubterolones are recently isolated glycosylated tropolonids with notable biological activity. They share similar aglycone skeletons but differ in their sugar moieties, and rubterolones in particular have a rare deoxysugar antiarose of unknown biosynthetic provenance. During our previously reported biosynthetic elucidation of the tropolone ring and pyridine moiety, gene inactivation experiments revealed that RubS3 is involved in sugar moiety biosynthesis. Here we report the in vitro characterization of RubS3 as a bifunctional reductase/epimerase catalyzing the formation of TDP-d-antiarose by epimerization at C3 and reduction at C4 of the key intermediate TDP-4-keto-6-deoxy-d-glucose. These new findings not only explain the biosynthetic pathway of deoxysugars in rubrolone-like natural products, but also introduce RubS3 as a new family of reductase/epimerase enzymes with potential to supply the rare antiarose unit for expanding the chemical space of glycosylated natural products. Rubrolones, isarubrolones, and rubterolones are recently isolated glycosylated tropolonids with notable biological activity.![]()
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Affiliation(s)
- Yijun Yan
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Jing Yang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Li Wang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Dongdong Xu
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Zhiyin Yu
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Xiaowei Guo
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
| | - Geoff P Horsman
- Department of Chemistry & Biochemistry, Wilfrid Laurier University Waterloo ON N2L 3C5 Canada
| | - Shuangjun Lin
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China
| | - Meifeng Tao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China
| | - Sheng-Xiong Huang
- State Key Laboratory of Phytochemistry and Plant Resources in West China, CAS Center for Excellence in Molecular Plant Sciences, Kunming Institute of Botany, Chinese Academy of Sciences Kunming 650201 China
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9
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Bergame CP, Dong C, Sutour S, von Reuß SH. Epimerization of an Ascaroside-Type Glycolipid Downstream of the Canonical β-Oxidation Cycle in the Nematode Caenorhabditis nigoni. Org Lett 2019; 21:9889-9892. [PMID: 31809061 DOI: 10.1021/acs.orglett.9b03808] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A species-specific ascaroside-type glycolipid was identified in the nematode Caenorhabditis nigoni using HPLC-ESI-(-)-MS/MS precursor ion scanning, HR-MS/MS, and NMR techniques. Its structure containing an l-3,6-dideoxy-lyxo-hexose unit was established by total synthesis. The identification of this novel 4-epi-ascaroside (caenorhabdoside) in C. nigoni along with the previous identification of 2-epi-ascarosides (paratosides) in Pristionchus pacificus indicate that nematodes can generate highly specific signaling molecules by epimerization of the ascarylose building block downstream of the canonical β-oxidation cycle.
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Affiliation(s)
- Célia P Bergame
- Laboratory for Bioanalytical Chemistry, Institute of Chemistry , University of Neuchâtel , Avenue de Bellevaux 51 , CH-2000 Neuchâtel , Switzerland
| | - Chuanfu Dong
- Department of Bioorganic Chemistry , Max Planck Institute for Chemical Ecology , Hans-Knöll Straße 8 , D-07745 Jena , Germany
| | - Sylvain Sutour
- Neuchâtel Platform for Analytical Chemistry (NPAC) , University of Neuchâtel , Avenue de Bellevaux 51 , CH-2000 Neuchâtel , Switzerland
| | - Stephan H von Reuß
- Laboratory for Bioanalytical Chemistry, Institute of Chemistry , University of Neuchâtel , Avenue de Bellevaux 51 , CH-2000 Neuchâtel , Switzerland.,Department of Bioorganic Chemistry , Max Planck Institute for Chemical Ecology , Hans-Knöll Straße 8 , D-07745 Jena , Germany.,Neuchâtel Platform for Analytical Chemistry (NPAC) , University of Neuchâtel , Avenue de Bellevaux 51 , CH-2000 Neuchâtel , Switzerland
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10
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Frey PA, Hegeman AD. Chemical and stereochemical actions of UDP-galactose 4-epimerase. Acc Chem Res 2013; 46:1417-26. [PMID: 23339688 DOI: 10.1021/ar300246k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Uridine(5')diphospho(1)α-D-galactose (UDP-gal) provides all galactosyl units in biologically synthesized carbohydrates. All healthy cells produce UDP-gal from uridine(5')diphospho(1)α-D-glucose (UDP-glc) by the action of UDP-galactose 4-epimerase (GalE). This Account provides our recent results describing unusual mechanistic features of this enzyme. Fully active GalE is dimeric and contains one tightly bound nicotinamide adenine dinucleotide (NAD) per subunit. The NAD undergoes reversible reduction to NADH in the chemical mechanism. GalE displays unusual enzymological, chemical, and stereochemical properties. These include practically irreversible binding of NAD, nonstereospecific hydride transfer, uridine nucleotide-induced activation of NAD, Tyr149 as a base catalyst, and [GalE-NADH]-oxidation in one-electron steps by one-electron acceptors. Early studies revealed that uridine(5')diphospho(1)α-D-4-ketopyranose (UDP-4-ketopyranose) and NADH are reaction intermediates. Weak binding of the 4-ketopyranosyl moiety and strong binding of the UDP-moiety allowed either face of the 4-ketopyranosyl moiety to accept hydride from NADH. In crystal structures of GalE, NAD bound within a Rossmann-type fold and uridine nucleotides within a substrate domain. Structures of [GalE-NADH] in complex with UDP-glc show Lys153, Tyr149, and Ser124 in contact with NAD or glucosyl-C4(OH). Lys153 forms hydrogen bonds to the ribosyl-OH groups of NAD. The phenolate of Tyr149 is associated with both the nicotinamide ring of NAD and glucosyl-C4(OH). Ser124 is hydrogen-bonded to glucosyl-C4(OH). Spectrophotometry studies show a pH-dependent charge transfer (CT) complex between Tyr149 and NAD. The CT-complex has a pKa of 6.1, which results in bleaching of the CT-band. The CT-band also bleaches upon binding of a uridine nucleotide. Kinetic experiments with wild-type GalE and Ser124Ala-GalE show the same kinetic pKa values as the corresponding CT-band pKa, which point to Tyr149 as the base catalyst for hydride transfer. We used NMR studies to verify that uridine nucleotide binding polarizes nicotinamide π-electrons. The binding of uridine(5')-diphosphate (UDP) to GalE-[nicotinamide-1-¹⁵N]NAD shifts the ¹⁵N-signal upfield 3 ppm, whereas UDP-binding to GalE-[nicotinamide-4-¹³C]NAD shifts the ¹³C-signal downfield by 3.4 ppm. Electrochemical and ¹³C NMR data for a series of N-alkylnicotinamides show that the 3.4 ppm downfield ¹³C-perturbation in GalE corresponds to an elevation of the NAD reduction potential by 150 mV. These results account for the uridine nucleotide-dependence in the reduction of [GalE-NAD] by glucose or NaBH₃CN. Kinetics in the reduction of Tyr149Phe- and Lys153Met-GalE-NAD implicate Tyr149 and Lys153 in the nucleotide-dependent reduction of NAD. They further implicate electrostatic repulsion between N1 of NAD and the ε-aminium group of Lys153 in nucleotide-induced activation of NAD. In an O₂-dependent reaction, [GalE-NADH] reduces the stable radical UDP-TEMPO with production of superoxide radical. The reaction must proceed by way of a NAD-pyridinyl radical intermediate.
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Affiliation(s)
- Perry A. Frey
- Department of Biochemistry, University of Wisconsin—Madison, 1710 University Avenue, Madison, Wisconsin 53705, United States
| | - Adrian D. Hegeman
- Department of Biochemistry, University of Wisconsin—Madison, 1710 University Avenue, Madison, Wisconsin 53705, United States
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11
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Choi SH, Ruszczycky MW, Zhang H, Liu HW. A fluoro analogue of UDP-α-D-glucuronic acid is an inhibitor of UDP-α-D-apiose/UDP-α-D-xylose synthase. Chem Commun (Camb) 2011; 47:10130-2. [PMID: 21826368 DOI: 10.1039/c1cc13140k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
UDP-2F-glucuronic acid was synthesized and analyzed as a mechanistic probe to investigate the ring contraction step catalyzed by UDP-d-apiose/UDP-d-xylose synthase (AXS).
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Affiliation(s)
- Sei-hyun Choi
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA
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12
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Yoo HG, Kwon SY, Karki S, Kwon HJ. A new route to dTDP-6-deoxy-l-talose and dTDP-L-rhamnose: dTDP-L-rhamnose 4-epimerase in Burkholderia thailandensis. Bioorg Med Chem Lett 2011; 21:3914-7. [PMID: 21640586 DOI: 10.1016/j.bmcl.2011.05.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 05/09/2011] [Accepted: 05/10/2011] [Indexed: 10/18/2022]
Abstract
dTDP-L-rhamnose (dTDP-Rha)-synthesizing dTDP-6-deoxy-L-lyxo-4-hexulose reductase (4-KR) and dTDP-Rha 4-epimerase were characterized from Burkholderia thailandensis E264 by utilizing rmlD(Bth) (BTH_I1472) and wbiB(Bth) (BTH_I1476), respectively. Incubation of the recombinant WbiB(Bth) with RmlA/RmlB/RmlC/Tal, which has previously been shown to generate dTDP-6-deoxy-L-talose (dTDP-6dTal) from α-D-glucose-1-phosphate, dTTP, and NADPH, produced dTDP-Rha. (1)H NMR measurements confirmed that both RmlA/RmlB/RmlC/Tal/WbiB(Bth) and RmlA/RmlB/RmlC/RmlD produced dTDP-Rha. WbiB(Bth) alone produced dTDP-Rha when incubated with dTDP-6dTal. This is the first report to demonstrate epimerase activity interconverting between dTDP-Rha and dTDP-6dTal.
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Affiliation(s)
- Hye-Gyeong Yoo
- Department of Biological Science, Division of Bioscience and Bioinformatics, Myongji University, Yongin 449-728, Republic of Korea
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13
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Diastereoselective synthesis of propargylic fluorides and its application in preparation of monofluorinated sugar. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.04.078] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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14
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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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15
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Transient oxidation as a mechanistic strategy in enzymatic catalysis. Curr Opin Chem Biol 2008; 12:532-8. [DOI: 10.1016/j.cbpa.2008.06.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Accepted: 06/17/2008] [Indexed: 11/18/2022]
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16
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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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17
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Thibodeaux CJ, Melançon CE, Liu HW. Unusual sugar biosynthesis and natural product glycodiversification. Nature 2007; 446:1008-16. [PMID: 17460661 DOI: 10.1038/nature05814] [Citation(s) in RCA: 250] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The enzymes involved in the biosynthesis of carbohydrates and the attachment of sugar units to biological acceptor molecules catalyse an array of chemical transformations and coupling reactions. In prokaryotes, both common sugar precursors and their enzymatically modified derivatives often become substituents of biologically active natural products through the action of glycosyltransferases. Recently, researchers have begun to harness the power of these biological catalysts to alter the sugar structures and glycosylation patterns of natural products both in vivo and in vitro. Biochemical and structural studies of sugar biosynthetic enzymes and glycosyltransferases, coupled with advances in bioengineering methodology, have ushered in a new era of drug development.
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Affiliation(s)
- Christopher J Thibodeaux
- Institute for Cellular and Molecular Biology, 1 University Station A4810, University of Texas at Austin, Austin, Texas 78712, USA
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18
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Morrison JP, Tanner ME. A two-base mechanism for Escherichia coli ADP-L-glycero-D-manno-heptose 6-epimerase. Biochemistry 2007; 46:3916-24. [PMID: 17316025 DOI: 10.1021/bi602641m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ADP-l-glycero-d-manno-heptose 6-epimerase (HldD or AGME, formerly RfaD) catalyzes the inversion of configuration at C-6' ' of the heptose moiety of ADP-d-glycero-d-manno-heptose and ADP-l-glycero-d-manno-heptose. The epimerase HldD operates in the biosynthetic pathway of l-glycero-d-manno-heptose, which is a conserved sugar in the core region of lipopolysaccharide (LPS) of Gram-negative bacteria. Previous studies support a mechanism in which HldD uses its tightly bound NADP+ cofactor to oxidize directly at C-6' ', generating a ketone intermediate. A reduction of the ketone from the opposite face then occurs, generating the epimeric product. How the epimerase is able access both faces of the ketone intermediate with correct alignment of the three required components, NADPH, the ketone carbonyl, and a catalytic acid/base residue, is addressed here. It is proposed that the epimerase active site contains two catalytic pockets, each of which bears a catalytic acid/base residue that facilitates reduction of the C-6' ' ketone but leads to a distinct epimeric product. The ketone carbonyl may access either pocket via rotation about the C-5' '-C-6' ' bond of the sugar nucleotide and in doing so presents opposing faces to the bound cofactor. Evidence in support of the two-base mechanism is found in studies of two single mutants of the Escherichia coli K-12 epimerase, Y140F and K178M, both of which have severely compromised epimerase activities that are more than 3 orders of magnitude lower than that of the wild type. The catalytic competency of these two mutants in promoting redox chemistry is demonstrated with an alternate catalytic activity that requires only one catalytic base: dismutation of a C-6' ' aldehyde substrate analogue (ADP-beta-d-manno-hexodialdose) to an acid and an alcohol (ADP-beta-d-mannuronic acid and ADP-beta-d-mannose). This study identifies the two catalytic bases as tyrosine 140 and lysine 178. A one-step enzymatic conversion of mannose into ADP-beta-mannose is also described and used to make C-6' '-substituted derivatives of this sugar nucleotide.
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Affiliation(s)
- James P Morrison
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
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19
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Read JA, Ahmed RA, Tanner ME. Efficient chemoenzymatic synthesis of ADP-D-glycero-beta-D-manno-heptose and a mechanistic study of ADP-L-glycero-D-manno-heptose 6-epimerase. Org Lett 2006; 7:2457-60. [PMID: 15932222 DOI: 10.1021/ol050774q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text] A chemoenzymatic synthesis of ADP-D-glycero-beta-D-manno-heptose (ADP-D,D-Hep) is described in which D,D-Hep 7-phosphate is converted to ADP-D,D-Hep by two biosynthetic enzymes. This strategy allows access to the 6''-deuterated analogue, which upon incubation with the epimerase showed complete retention of the isotopic label at the 6''-position. This provides evidence for a direct oxidation mechanism in which the hydride initially transferred to the NADP+ cofactor is subsequently returned to the same carbon in a nonstereospecific manner.
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Affiliation(s)
- Jay A Read
- Department of Chemistry, University of British Columbia, Vancouver, BC, Canada
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20
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Morrison JP, Read JA, Coleman WG, Tanner ME. Dismutase activity of ADP-L-glycero-D-manno-heptose 6-epimerase: evidence for a direct oxidation/reduction mechanism. Biochemistry 2005; 44:5907-15. [PMID: 15823050 DOI: 10.1021/bi050106c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first positive evidence for the utilization of a direct C-6' ' oxidation/reduction mechanism by ADP-l-glycero-d-manno-heptose 6-epimerase is reported here. The epimerase (HldD or AGME, formerly RfaD) operates in the biosynthetic pathway of l-glycero-d-manno-heptose, which is a conserved sugar in the core region of lipopolysaccharide (LPS) of Gram-negative bacteria. The stereochemical inversion catalyzed by the epimerase is interesting as it occurs at an "unactivated" stereocenter that lacks an acidic C-H bond, and therefore, a direct deprotonation/reprotonation mechanism cannot be employed. Instead, the epimerase employs a transient oxidation strategy involving a tightly bound NADP(+) cofactor. A recent study ruled out mechanisms involving transient oxidation at C-4' ' and C-7' ' and supported a mechanism that involves an initial oxidation directly at the C-6' ' position to generate a 6' '-keto intermediate (Read, J. A., Ahmed, R. A., Morrison, J. P., Coleman, W. G., Jr., Tanner, M. E. (2004) J. Am. Chem. Soc. 126, 8878-8879). A subsequent nonstereospecific reduction of the ketone intermediate can generate either epimer of the ADP-heptose. In this work, an intermediate analogue containing an aldehyde functionality at C-6' ', ADP-beta-d-manno-hexodialdose, is prepared in order to probe the ability of the enzyme to catalyze redox chemistry at this position. It is found that incubation of the aldehyde with a catalytic amount of the epimerase leads to a dismutation process in which one-half of the material is oxidized to ADP-beta-d-mannuronic acid and the other half is reduced to ADP-beta-d-mannose. Transient reduction of the enzyme-bound NADP(+) was monitored by UV spectroscopy and implicates the cofactor's involvement during catalysis.
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Affiliation(s)
- James P Morrison
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
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21
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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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22
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Koropatkin NM, Liu HW, Holden HM. High resolution x-ray structure of tyvelose epimerase from Salmonella typhi. J Biol Chem 2003; 278:20874-81. [PMID: 12642575 DOI: 10.1074/jbc.m301948200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyvelose epimerase catalyzes the last step in the biosynthesis of tyvelose by converting CDP-d-paratose to CDP-d-tyvelose. This unusual 3,6-dideoxyhexose occurs in the O-antigens of some types of Gram-negative bacteria. Here we describe the cloning, protein purification, and high-resolution x-ray crystallographic analysis of tyvelose epimerase from Salmonella typhi complexed with CDP. The enzyme from S. typhi is a homotetramer with each subunit containing 339 amino acid residues and a tightly bound NAD+ cofactor. The quaternary structure of the enzyme displays 222 symmetry and can be aptly described as a dimer of dimers. Each subunit folds into two distinct lobes: the N-terminal motif responsible for NAD+ binding and the C-terminal region that harbors the binding site for CDP. The analysis described here demonstrates that tyvelose epimerase belongs to the short-chain dehydrogenase/reductase superfamily of enzymes. Indeed, its active site is reminiscent to that observed for UDP-galactose 4-epimerase, an enzyme that plays a key role in galactose metabolism. Unlike UDP-galactose 4-epimerase where the conversion of configuration occurs about C-4 of the UDP-glucose or UDP-galactose substrates, in the reaction catalyzed by tyvelose epimerase, the inversion of stereochemistry occurs at C-2. On the basis of the observed binding mode for CDP, it is possible to predict the manner in which the substrate, CDP-paratose, and the product, CDP-tyvelose, might be accommodated within the active site of tyvelose epimerase.
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Affiliation(s)
- Nicole M Koropatkin
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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23
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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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24
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Zhao Z, Liu H. Synthesis of a deoxysugar dinucleotide containing an exo-difluoromethylene moiety as a mechanistic probe for studying enzymes involved in unusual sugar biosynthesis. J Org Chem 2001; 66:6810-5. [PMID: 11578241 DOI: 10.1021/jo0103672] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Z Zhao
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA.
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25
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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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26
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He X, Agnihotri G, Liu Hw HW. Novel enzymatic mechanisms in carbohydrate metabolism. Chem Rev 2000; 100:4615-62. [PMID: 11749360 DOI: 10.1021/cr9902998] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- X He
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
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