1
|
Dulin CC, Sharma P, Frigo L, Voehler MW, Iverson TM, Bachmann BO. EvdS6 is a bifunctional decarboxylase from the everninomicin gene cluster. J Biol Chem 2023:104893. [PMID: 37286037 PMCID: PMC10338323 DOI: 10.1016/j.jbc.2023.104893] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/25/2023] [Accepted: 05/29/2023] [Indexed: 06/09/2023] Open
Abstract
The everninomicins are bacterially produced antibiotic octasaccharides characterized by the presence of two interglycosidic spirocyclic ortho-δ-lactone (orthoester) moieties. The terminating G- and H-ring sugars, L-lyxose and C-4 branched sugar β-D-eurekanate, are proposed to be biosynthetically derived from nucleotide diphosphate pentose sugar pyranosides; however, the identity of these precursors and their biosynthetic origin remain to be determined. Herein we identify a new glucuronic acid decarboxylase from Micromonospora belonging to the superfamily of short-chain dehydrogenase/reductase enzymes, EvdS6. Biochemical characterization demonstrated that EvdS6 is an NAD+-dependent bifunctional enzyme that produces a mixture of two products, differing in the sugar C-4 oxidation state. This product distribution is atypical for glucuronic acid decarboxylating enzymes, most of which favor production of the reduced sugar and a minority of which favor release of the oxidized product. Spectroscopic and stereochemical analysis of reaction products revealed that the first product released is the oxidatively produced 4-keto-D-xylose and the second product is the reduced D-xylose. X-ray crystallographic analysis of EvdS6 at 1.51 Å resolution with bound co-factor and TDP demonstrated that the overall geometry of the EvdS6 active site is conserved with other SDR enzymes and enabled studies probing structural determinants for the reductive half of the net neutral catalytic cycle. Critical active site threonine and aspartate residues were unambiguously identified as essential in the reductive step of the reaction and resulted in enzyme variants producing almost exclusively the keto sugar. This work defines potential precursors for the G-ring L-lyxose and resolves likely origins of the H-ring β-D-eurekanate sugar precursor.
Collapse
Affiliation(s)
- Callie C Dulin
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Pankaj Sharma
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Laura Frigo
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Markus W Voehler
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - T M Iverson
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA; Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Brian O Bachmann
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA; Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
2
|
Wang Q, Cai L, Zhang R, Wei S, Li F, Liu Y, Xu Y. A Unique Set of Auxiliary Metabolic Genes Found in an Isolated Cyanophage Sheds New Light on Marine Phage-Host Interactions. Microbiol Spectr 2022; 10:e0236722. [PMID: 36190421 PMCID: PMC9602691 DOI: 10.1128/spectrum.02367-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 09/10/2022] [Indexed: 01/04/2023] Open
Abstract
Cyanophages, viruses that infect cyanobacteria, are abundant and widely distributed in aquatic ecosystems, playing important roles in regulating the abundance, activity, diversity, and evolution of cyanobacteria. A T4-like cyanophage, S-SCSM1, infecting Synechococcus and Prochlorococcus strains of different ecotypes, was isolated from the South China Sea in this study. For the first time, a mannose-6-phosphate isomerase (MPI) gene was identified in the cultured cyanophage. At least 11 phylogenetic clusters of cyanophage MPIs were retrieved and identified from the marine metagenomic data sets, indicating that cyanophage MPIs in the marine environment are extremely diverse. The existence of 24 genes encoding 2-oxoglutarate (2OG)-Fe(II) oxygenase superfamily proteins in the S-SCSM1 genome emphasizes their potential importance and diverse functions in reprogramming host metabolism during phage infection. Novel cell wall synthesis and modification genes found in the S-SCSM1 genome indicate that diverse phenotypic modifications imposed by phages on cyanobacterial hosts remain to be discovered. Two noncoding RNAs of cis-regulatory elements in the S-SCSM1 genome were predicted to be associated with host exopolysaccharide metabolism and photosynthesis. The isolation and genomic characterization of cyanophage S-SCSM1 provide more information on the genetic diversity of cyanophages and phage-host interactions in the marine environment. IMPORTANCE Cyanophages play important ecological roles in aquatic ecosystems. Genomic and proteomic characterizations of the T4-like cyanophage S-SCSM1 indicate that novel and diverse viral genes and phage-host interactions in the marine environment remain unexplored. The first identified mannose-6-phosphate isomerase (MPI) gene from a cultured cyanophage was found in the S-SCSM1 genome, although MPIs were previously found in viral metagenomes at high frequencies similar to those of the cyanophage photosynthetic gene psbA. The presence of 24 genes encoding 2-oxoglutarate (2OG)-Fe(II) oxygenase superfamily proteins, novel cell wall synthesis and modification genes, a nonbleaching protein A gene, and 2 noncoding RNAs of cis-regulatory elements in the S-SCSM1 genome as well as the presence of a virion-associated regulatory protein indicate the diverse functions that cyanophages have in reprogramming the metabolism and modifying the phenotypes of hosts during infection.
Collapse
Affiliation(s)
- Qiong Wang
- Institute of Marine Science and Technology, Shandong University, Qingdao, People’s Republic of China
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, People’s Republic of China
| | - Lanlan Cai
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, People’s Republic of China
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, People’s Republic of China
| | - Rui Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, People’s Republic of China
| | - Shuzhen Wei
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, People’s Republic of China
| | - Fang Li
- State Key Laboratory Breeding Base of Marine Genetic Resource, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, People’s Republic of China
| | - Yuanfang Liu
- Institute of Marine Science and Technology, Shandong University, Qingdao, People’s Republic of China
| | - Yongle Xu
- Institute of Marine Science and Technology, Shandong University, Qingdao, People’s Republic of China
| |
Collapse
|
3
|
Beerens K, Gevaert O, Desmet T. GDP-Mannose 3,5-Epimerase: A View on Structure, Mechanism, and Industrial Potential. Front Mol Biosci 2022; 8:784142. [PMID: 35087867 PMCID: PMC8787198 DOI: 10.3389/fmolb.2021.784142] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/20/2021] [Indexed: 11/13/2022] Open
Abstract
GDP-mannose 3,5-epimerase (GM35E, GME) belongs to the short-chain dehydrogenase/reductase (SDR) protein superfamily and catalyses the conversion of GDP-d-mannose towards GDP-l-galactose. Although the overall reaction seems relatively simple (a double epimerization), the enzyme needs to orchestrate a complex set of chemical reactions, with no less than 6 catalysis steps (oxidation, 2x deprotonation, 2x protonation and reduction), to perform the double epimerization of GDP-mannose to GDP-l-galactose. The enzyme is involved in the biosynthesis of vitamin C in plants and lipopolysaccharide synthesis in bacteria. In this review, we provide a clear overview of these interesting epimerases, including the latest findings such as the recently characterized bacterial and thermostable GM35E representative and its mechanism revision but also focus on their industrial potential in rare sugar synthesis and glycorandomization.
Collapse
Affiliation(s)
| | | | - Tom Desmet
- *Correspondence: Koen Beerens, ; Tom Desmet,
| |
Collapse
|
4
|
Alvarez Quispe C, Da Costa M, Beerens K, Desmet T. Exploration of archaeal nucleotide sugar epimerases unveils a new and highly promiscuous GDP-Gal4E subgroup. CURRENT RESEARCH IN BIOTECHNOLOGY 2022. [DOI: 10.1016/j.crbiot.2022.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
5
|
Suresh A, Shravan Ramgopal D, Panchamoorthy Gopinath K, Arun J, SundarRajan P, Bhatnagar A. Recent advancements in the synthesis of novel thermostable biocatalysts and their applications in commercially important chemoenzymatic conversion processes. BIORESOURCE TECHNOLOGY 2021; 323:124558. [PMID: 33383359 DOI: 10.1016/j.biortech.2020.124558] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/11/2020] [Accepted: 12/12/2020] [Indexed: 06/12/2023]
Abstract
Thermostable enzymes are a field of growing interest in bioremediation, pharmaceuticals, food industry etc., due to their ability to catalyze bio reactions at high temperatures. This review aims to provide an overview on extremophiles with a special focus on thermophiles and enzymes produced from extremophilic bacteria. Novel thermostable catalysts, used in producing commercially important chemicals, are discussed in this review. Various classes of enzymes produced by microbes, synthesis of thermozymes and comparison with enzymes produced at optimal conditions are critically discussed. A detailed discussion on immobilized enzymes in comparisons with free enzymes, produced by extremozymes, is included. Different parameters which affect enzyme production are also discussed. The current industrial trends along with the future of biocatalysts in the production of chemicals using efficient methods are also discussed.
Collapse
Affiliation(s)
- Aravind Suresh
- Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam - 603110, Chennai, Tamil Nadu, India
| | - Dhakshin Shravan Ramgopal
- Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam - 603110, Chennai, Tamil Nadu, India
| | - Kannappan Panchamoorthy Gopinath
- Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam - 603110, Chennai, Tamil Nadu, India
| | - Jayaseelan Arun
- Centre for Waste Management, International Research Centre, Sathyabama Institute of Science and Technology, Jeppiaar Nagar (OMR), Chennai 600119, Tamil Nadu, India
| | - Panneerselvam SundarRajan
- Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Kalavakkam - 603110, Chennai, Tamil Nadu, India
| | - Amit Bhatnagar
- Department of Separation Science, LUT School of Engineering Science, LUT University, Sammonkatu 12, FI-50130 Mikkeli, Finland.
| |
Collapse
|
6
|
Da Costa M, Gevaert O, Van Overtveldt S, Lange J, Joosten HJ, Desmet T, Beerens K. Structure-function relationships in NDP-sugar active SDR enzymes: Fingerprints for functional annotation and enzyme engineering. Biotechnol Adv 2021; 48:107705. [PMID: 33571638 DOI: 10.1016/j.biotechadv.2021.107705] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 12/18/2020] [Accepted: 01/27/2021] [Indexed: 12/12/2022]
Abstract
Short-chain Dehydrogenase/Reductase enzymes that are active on nucleotide sugars (abbreviated as NS-SDR) are of paramount importance in the biosynthesis of rare sugars and glycosides. Some family members have already been extensively characterized due to their direct implication in metabolic disorders or in the biosynthesis of virulence factors. In this review, we combine the knowledge gathered from studies that typically focused only on one NS-SDR activity with an in-depth analysis and overview of all of the different NS-SDR families (169,076 enzyme sequences). Through this structure-based multiple sequence alignment of NS-SDRs retrieved from public databases, we could identify clear patterns in conservation and correlation of crucial residues. Supported by this analysis, we suggest updating and extending the UDP-galactose 4-epimerase "hexagonal box model" to an "heptagonal box model" for all NS-SDR enzymes. This specificity model consists of seven conserved regions surrounding the NDP-sugar substrate that serve as fingerprint for each specificity. The specificity fingerprints highlighted in this review will be beneficial for functional annotation of the large group of NS-SDR enzymes and form a guide for future enzyme engineering efforts focused on the biosynthesis of rare and specialty carbohydrates.
Collapse
Affiliation(s)
- Matthieu Da Costa
- Centre for Synthetic Biology - Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium
| | - Ophelia Gevaert
- Centre for Synthetic Biology - Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium
| | - Stevie Van Overtveldt
- Centre for Synthetic Biology - Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium
| | - Joanna Lange
- Bio-Prodict BV, Nieuwe Marktstraat 54E, 6511, AA, Nijmegen, the Netherlands
| | - Henk-Jan Joosten
- Bio-Prodict BV, Nieuwe Marktstraat 54E, 6511, AA, Nijmegen, the Netherlands
| | - Tom Desmet
- Centre for Synthetic Biology - Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium.
| | - Koen Beerens
- Centre for Synthetic Biology - Unit for Biocatalysis and Enzyme Engineering, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium.
| |
Collapse
|
7
|
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.
Collapse
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.
| |
Collapse
|
8
|
Gevaert O, Van Overtveldt S, Da Costa M, Beerens K, Desmet T. GDP-altrose as novel product of GDP-mannose 3,5-epimerase: Revisiting its reaction mechanism. Int J Biol Macromol 2020; 165:1862-1868. [PMID: 33075338 DOI: 10.1016/j.ijbiomac.2020.10.067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 10/08/2020] [Accepted: 10/09/2020] [Indexed: 10/23/2022]
Abstract
GDP-mannose 3,5-epimerase (GM35E) catalyzes the double epimerization of GDP-mannose to yield GDP-l-galactose. GDP-l-gulose (C5-epimer) has previously been detected as a byproduct of this reaction, indicating that C3,5-epimerization occurs through an initial epimerization at C5. Given these products, GM35E constitutes a valuable bridge between d- and l-hexoses. In order to fully exploit this potential, the enzyme might be subjected to specificity engineering for which profound mechanistic insights are beneficial. Accordingly, this study further elucidated GM35E's reaction mechanism. For the first time, the production of the C3-epimer GDP-altrose was demonstrated, resulting in an adjustment of the acknowledged reaction mechanism. As GM35E converts GDP-mannose to GDP-l-gulose, GDP-altrose and GDP-l-galactose in a 72:4:4:20 ratio, this indicates that the enzyme does not discriminate between the C3 and C5 position as initial epimerization site. This was also confirmed by a structural investigation. Based on a mutational analysis of the active site, residues S115 and R281 were attributed a stabilizing function, which is believed to support the reactivation process of the catalytic residues. This paper eventually reflected on some engineering strategies that aim to change the enzyme towards a single specificity.
Collapse
Affiliation(s)
- Ophelia Gevaert
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Stevie Van Overtveldt
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Matthieu Da Costa
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Koen Beerens
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Tom Desmet
- Centre for Synthetic Biology, Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Bearne SL. Through the Looking Glass: Chiral Recognition of Substrates and Products at the Active Sites of Racemases and Epimerases. Chemistry 2020; 26:10367-10390. [DOI: 10.1002/chem.201905826] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/09/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Stephen L. Bearne
- Department of Biochemistry & Molecular BiologyDepartment of ChemistryDalhousie University Halifax, Nova Scotia B3H 4R2 Canada
| |
Collapse
|
11
|
Novel Insights into the Existence of the Putative UDP-Glucuronate 5-Epimerase Specificity. Catalysts 2020. [DOI: 10.3390/catal10020222] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
C5-epimerases are promising tools for the production of rare l-hexoses from their more common d-counterparts. On that account, UDP-glucuronate 5-epimerase (UGA5E) attracts attention as this enzyme could prove to be useful for the synthesis of UDP-l-iduronate. Interestingly, l-iduronate is known as a precursor for the production of heparin, an effective anticoagulant. To date, the UGA5E specificity has only been detected in rabbit skin extract, and the respective enzyme has not been characterized in detail or even identified at the molecular level. Accordingly, the current work aimed to shed more light on the properties of UGA5E. Therefore, the pool of putative UGA5Es present in the UniProt database was scrutinized and their sequences were clustered in a phylogenetic tree. However, the examination of two of these enzymes revealed that they actually epimerize UDP-glucuronate at the 4- rather than 5-position. Furthermore, in silico analysis indicated that this should be the case for all sequences that are currently annotated as UGA5E and, hence, that such activity has not yet been discovered in nature. The detected l-iduronate synthesis in rabbit skin extract can probably be assigned to the enzyme chondroitin-glucuronate C5-epimerase, which catalyzes the conversion of d-glucuronate to l-iduronate on a polysaccharide level.
Collapse
|