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Sato S, Fan PH, Yeh YC, Liu HW. Complete In Vitro Reconstitution of the Apramycin Biosynthetic Pathway Demonstrates the Unusual Incorporation of a β-d-Sugar Nucleotide in the Final Glycosylation Step. J Am Chem Soc 2024; 146:10103-10114. [PMID: 38546392 DOI: 10.1021/jacs.4c01233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Apramycin is a widely used aminoglycoside antibiotic with applications in veterinary medicine. It is composed of a 4-amino-4-deoxy-d-glucose moiety and the pseudodisaccharide aprosamine, which is an adduct of 2-deoxystreptamine and an unusual eight-carbon bicyclic dialdose. Despite its extensive study and relevance to medical practice, the biosynthetic pathway of this complex aminoglycoside nevertheless remains incomplete. Herein, the remaining unknown steps of apramycin biosynthesis are reconstituted in vitro, thereby leading to a comprehensive picture of its biological assembly. In particular, phosphomutase AprJ and nucleotide transferase AprK are found to catalyze the conversion of glucose 6-phosphate to NDP-β-d-glucose as a critical biosynthetic intermediate. Moreover, the dehydrogenase AprD5 and transaminase AprL are identified as modifying this intermediate via introduction of an amino group at the 4″ position without requiring prior 6″-deoxygenation as is typically encountered in aminosugar biosynthesis. Finally, the glycoside hydrolase family 65 protein AprO is shown to utilize NDP-β-d-glucose or NDP-4"-amino-4"-deoxy-β-d-glucose to form the 8',1″-O-glycosidic linkage of saccharocin or apramycin, respectively. As the activated sugar nucleotides in all known natural glycosylation reactions involve either NDP-α-d-hexoses or NDP-β-l-hexoses, the reported chemistry expands the scope of known biological glycosylation reactions to NDP-β-d-hexoses, with important implications for the understanding and repurposing of aminoglycoside biosynthesis.
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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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Xiang DF, Xu M, Ghosh MK, Raushel FM. Metabolic Pathways for the Biosynthesis of Heptoses Used in the Construction of Capsular Polysaccharides in the Human Pathogen Campylobacter jejuni. Biochemistry 2023; 62:3145-3158. [PMID: 37890137 PMCID: PMC10680097 DOI: 10.1021/acs.biochem.3c00390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/11/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023]
Abstract
Campylobacter jejuni is the leading cause of food poisoning in North America. The exterior surface of this bacterium is coated with a capsular polysaccharide (CPS) that consists of a repeating sequence of 2-5 different carbohydrates that is anchored to the outer membrane. Heptoses of various configurations are among the most common monosaccharides that have been identified within the CPS. It is currently thought that all heptose variations derive from the modification of GDP-d-glycero-α-d-manno-heptose (GMH). From the associated gene clusters for CPS biosynthesis, we have identified 20 unique enzymes with different substrate profiles that are used by the various strains and serotypes of C. jejuni to make six different stereoisomers of GDP-6-deoxy-heptose, four stereoisomers of GDP-d-glycero-heptoses, and two stereoisomers of GDP-3,6-dideoxy-heptoses starting from d-sedoheptulose-7-phosphate. The modification enzymes include a C4-dehydrogenase, a C4,6-dehydratase, three C3- and/or C5-epimerases, a C3-dehydratase, eight C4-reductases, two pyranose/furanose mutases, and four enzymes for the formation of GMH from d-sedoheptulose-7-phosphate. We have mixed these enzymes in different combinations to make novel GDP-heptose modifications, including GDP-6-hydroxy-heptoses, GDP-3-deoxy-heptoses, and GDP-3,6-dideoxy-heptoses.
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Affiliation(s)
- Dao Feng Xiang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Maggie Xu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Manas K. Ghosh
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Frank M. Raushel
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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Lee HJ, Lee SM, Choi M, Kwon JH, Lee SW. A Mutation of a Putative NDP-Sugar Epimerase Gene in Ralstonia pseudosolanacearum Attenuates Exopolysaccharide Production and Bacterial Virulence in Tomato Plant. THE PLANT PATHOLOGY JOURNAL 2023; 39:417-429. [PMID: 37817490 PMCID: PMC10580051 DOI: 10.5423/ppj.oa.06.2023.0090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/18/2023] [Accepted: 08/21/2023] [Indexed: 10/12/2023]
Abstract
Ralstonia solanacearum species complex (RSSC) is a soil borne plant pathogen causing bacterial wilt on various important crops, including Solanaceae plants. The bacterial pathogens within the RSSC produce exopolysaccharide (EPS), a highly complicated nitrogen-containing heteropolymeric polysaccharide, as a major virulence factor. However, the biosynthetic pathway of the EPS in the RSSC has not been fully characterized. To identify genes in EPS production beyond the EPS biosynthetic gene operon, we selected the EPS-defective mutants of R. pseudosolanacearum strain SL341 from Tn5-inserted mutant pool. Among several EPS-defective mutants, we identified a mutant, SL341P4, with a Tn5-insertion in a gene encoding a putative NDP-sugar epimerase, a putative membrane protein with sugar-modifying moiety, in a reverse orientation to EPS biosynthesis gene cluster. This protein showed similar to other NDP-sugar epimerases involved in EPS biosynthesis in many phytopathogens. Mutation of the NDP-sugar epimerase gene reduced EPS production and biofilm formation in R. pseudosolanacearum. Additionally, the SL341P4 mutant exhibited reduced disease severity and incidence of bacterial wilt in tomato plants compared to the wild-type SL341 without alteration of bacterial multiplication. These results indicate that the NDP-sugar epimerase gene is required for EPS production and bacterial virulence in R. pseudosolanacearum.
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Affiliation(s)
- Hyoung Ju Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Sang-Moo Lee
- Institute of Agricultural Life Sciences, Dong-A University, Busan 49315, Korea
| | - Minseo Choi
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Joo Hwan Kwon
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Seon-Woo Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
- Institute of Agricultural Life Sciences, Dong-A University, Busan 49315, Korea
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Qi S, Dong S, Fan M, Xue X, Wu L, Wang P. Stress Response in the Honeybee ( Apis mellifera L.) Gut Induced by Chlorinated Paraffins at Residue Levels Found in Bee Products. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:11442-11451. [PMID: 37490655 DOI: 10.1021/acs.est.3c01827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Chlorinated paraffins (CPs) have become global pollutants and are of considerable concern as a result of their persistence and long-distance transmission in the environment and toxicity to mammals. However, their risks to pollinating insects are unknown. Honeybees are classical pollinators and sensitive indicators of environmental pollution. Herein, the effects of CPs on the gut microenvironment and underlying mechanisms were evaluated and explored using Apis mellifera L. Both short- and medium-chain CPs had significant sublethal effects on honeybees at a residue dose of 10 mg/L detected in bee products but did not significantly alter the composition or diversity of the gut microbiota. However, this concentration did induce significant immune, detoxification, and antioxidation responses and metabolic imbalances in the midgut. The mechanisms of CP toxicity in bees are complicated by the complex composition of these chemicals, but this study indicated that CPs could substantially affect intestinal physiology and metabolic homeostasis. Therefore, CPs in the environment could have long-lasting impacts on bee health. Future studies are encouraged to identify novel bioindicators of CP exposure to detect early contamination and uncover the detailed mechanisms underlying the adverse effects of CPs on living organisms, especially pollinating insects.
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Affiliation(s)
- Suzhen Qi
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, People's Republic of China
| | - Shujun Dong
- Institute of Quality Standards and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, People's Republic of China
| | - Man Fan
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, People's Republic of China
- College of Animal Sciences (College of Bee Science), Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, People's Republic of China
| | - Xiaofeng Xue
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, People's Republic of China
| | - Liming Wu
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, People's Republic of China
| | - Peilong Wang
- Institute of Quality Standards and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, People's Republic of China
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Kurzylewska M, Bomba A, Dworaczek K, Pękala-Safińska A, Turska-Szewczuk A. Structure and gene cluster annotation of the O-antigen of Aeromonas sobria strain K928 isolated from common carp and classified into the new Aeromonas PGO1 serogroup. Carbohydr Res 2023; 528:108809. [PMID: 37086562 DOI: 10.1016/j.carres.2023.108809] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/05/2023] [Accepted: 04/05/2023] [Indexed: 04/24/2023]
Abstract
Aeromonas sobria strain K928 was isolated from a common carp during a Motile Aeromonas Infection/Motile Aeromonas Septicaemia disease outbreak on a Polish fish farm and classified into the new provisional PGO1 serogroup. The lipopolysaccharide of A. sobria K928 was subjected to mild acid hydrolysis, and the O-specific polysaccharide, which was isolated by gel-permeation chromatography, was studied using sugar and methylation analyses and 1H and 13C NMR spectroscopy. The following structure of the branched O-specific polysaccharide repeating unit of A. sobria K928 was established. →2)[α-D-Fucp3NRHb-(1→3)]-α-L-Rhap-(1→3)-β-L-Rhap-(1→4)-α-L-Rhap-(1→3)-β-D-FucpNAc-(1→ The O-antigen gene cluster was identified and characterized in the genome of the A. sobria K928 strain after comparison with sequences in the available databases. The composition of the O-antigen genetic region was found to be consistent with the O-polysaccharide structure, and its organization was proposed.
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Affiliation(s)
- Maria Kurzylewska
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland
| | - Arkadiusz Bomba
- Department of Omics Analyses, National Veterinary Research Institute, Partyzantow 57, 24-100, Pulawy, Poland
| | - Katarzyna Dworaczek
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland
| | - Agnieszka Pękala-Safińska
- Department of Preclinical Sciences and Infectious Diseases, Faculty of Veterinary Medicine and Animal Science, Poznan University of Life Sciences, Wolynska 35, 60-637, Poznan, Poland
| | - Anna Turska-Szewczuk
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland.
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Lee JH, Kang HI, Kim S, Ahn YB, Kim H, Hong JK, Baik JY. NAD + supplementation improves mAb productivity in CHO cells via a glucose metabolic shift. Biotechnol J 2023; 18:e2200570. [PMID: 36717516 DOI: 10.1002/biot.202200570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 12/22/2022] [Accepted: 01/19/2023] [Indexed: 02/01/2023]
Abstract
Aerobic glycolysis and its by-product lactate accumulation are usually associated with adverse culture phenotypes such as poor cell viability and productivity. Due to the lack of knowledge on underlying mechanisms and accompanying biological processes, the regulation of aerobic glycolysis has been an ongoing challenge in culture process development for therapeutic protein productivity. Nicotinamide adenine dinucleotide (NAD+ ), a coenzyme and co-substrate in energy metabolism, promotes the conversion of inefficient glycolysis into an efficient oxidative phosphorylation (OXPHOS) pathway. However, the effect of NAD+ on Chinese hamster ovary (CHO) cells for biopharmaceutical production has not been reported yet. In this work, we aimed to elucidate the influence of NAD+ on cell culture performance by examining metabolic shifts and mAb productivity. The supplementation of NAD+ increased the intracellular concentration of NAD+ and promoted SIRT3 expression. Antibody titer and the specific productivity in the growth phase were improved by up to 1.82- and 1.88-fold, respectively, with marginal restrictions on cell growth. NAD+ significantly reduced the accumulation of reactive oxygen species (ROS) and the lactate yield from glucose, determined by lactate accumulation versus glucose consumption (YLAC/GLC ). In contrast, OXPHOS capacity and amino acid consumption rate increased substantially. Collectively, these results suggest that NAD+ contributes to improving therapeutic protein productivity in bioprocessing via inducing an energy metabolic shift.
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Affiliation(s)
- Ji Hwan Lee
- Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Hye-Im Kang
- Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Suheon Kim
- Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Yeong Bin Ahn
- Division of Biological Science and Technology, Yonsei University, Wonju, Gangwon-do, Republic of Korea
| | - Hagyeong Kim
- Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
| | - Jong Kwang Hong
- Division of Biological Science and Technology, Yonsei University, Wonju, Gangwon-do, Republic of Korea
| | - Jong Youn Baik
- Department of Biological Sciences and Bioengineering, Inha University, Incheon, South Korea
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A colorimetric assay for the screening and kinetic analysis of nucleotide sugar 4,6-dehydratases. Anal Biochem 2022; 655:114870. [PMID: 36027972 DOI: 10.1016/j.ab.2022.114870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 08/12/2022] [Accepted: 08/16/2022] [Indexed: 11/22/2022]
Abstract
Nucleotide sugar 4,6-dehydratases belong to the Short-chain Dehydrogenase/Reductase (SDR) superfamily and catalyze the conversion of an NDP-hexose to an NDP-4-keto-6-deoxy hexose, a key step in the biosynthesis of a plethora of deoxy and amino sugars. Here, we present a colorimetric assay for the detection of their reaction products (NDP-4-keto-6-deoxy hexoses) using concentrated sulfuric acid and an ethanolic resorcinol solution. Under these conditions, the keto-function of the dehydratase product reacts specifically with resorcinol to form an orange-red or pink complex for NDP-glucose/GDP-mannose and UDP-N-acetylglucosamine, respectively, with an absorption maximum at 510 nm. The presented assay allows reliable product detection at low concentrations and can be applied in microtiter plates. It thus allows the determination of kinetic enzyme parameters like the optimal temperature, pH, Vmax, KM and kcat, as well as the miniaturization for screening purposes with crude cell extracts. As such, this detection assay opens new possibilities for the characterization and screening of these dehydratases in 96-well plates for different research goals.
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Radzieta M, Malone M, Ahmad M, Dickson HG, Schwarzer S, Jensen SO, Lavery LA. Metatranscriptome sequencing identifies Escherichia are major contributors to pathogenic functions and biofilm formation in diabetes related foot osteomyelitis. Front Microbiol 2022; 13:956332. [PMID: 35979499 PMCID: PMC9376677 DOI: 10.3389/fmicb.2022.956332] [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: 05/30/2022] [Accepted: 07/11/2022] [Indexed: 11/26/2022] Open
Abstract
Osteomyelitis in the feet of persons with diabetes is clinically challenging and is associated with high rates of amputation. In this study RNA-sequencing was employed to explore microbial metatranscriptomes with a view to understand the relative activity and functions of the pathogen/s responsible for diabetes foot osteomyelitis (DFO). We obtained 25 intraoperative bone specimens from persons with confirmed DFO, observing that Escherichia spp. (7%), Streptomyces spp. (7%), Staphylococcus spp. (6%), Klebsiella spp. (5%) and Proteus spp. (5%) are the most active taxa on average. Data was then subset to examine functions associated with pathogenesis (virulence and toxins), biofilm formation and antimicrobial/multi-drug resistance. Analysis revealed Escherichia spp. are the most active taxa relative to pathogenic functions with K06218 (mRNA interferase relE), K03699 (membrane damaging toxin tlyC) and K03980 (putative peptidoglycan lipid II flippase murJ), K01114 (membrane damaging toxin plc) and K19168 (toxin cptA) being the most prevalent pathogenic associated transcripts. The most abundant transcripts associated with biofilm pathways included components of the biofilm EPS matrix including glycogen synthesis, cellulose synthesis, colonic acid synthesis and flagella synthesis. We further observed enrichment of a key enzyme involved in the biosynthesis of L-rhamnose (K01710 -dTDP-glucose 4,6-dehydratase rfbB, rmlB, rffG) which was present in all but four patients with DFO.
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Affiliation(s)
- Michael Radzieta
- South West Sydney Limb Preservation and Wound Research, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
- Infectious Diseases and Microbiology, School of Medicine, Western Sydney University, Sydney, NSW, Australia
| | - Matthew Malone
- South West Sydney Limb Preservation and Wound Research, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
- Infectious Diseases and Microbiology, School of Medicine, Western Sydney University, Sydney, NSW, Australia
- *Correspondence: Matthew Malone
| | - Mehtab Ahmad
- Department of Vascular Surgery, Liverpool Hospital, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
| | - Hugh G. Dickson
- South West Sydney Limb Preservation and Wound Research, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
- South Western Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Saskia Schwarzer
- South West Sydney Limb Preservation and Wound Research, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
- Infectious Diseases and Microbiology, School of Medicine, Western Sydney University, Sydney, NSW, Australia
| | - Slade O. Jensen
- South West Sydney Limb Preservation and Wound Research, South Western Sydney Local Health District (LHD), Sydney, NSW, Australia
- South Western Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Lawrence A. Lavery
- Department of Plastic Surgery, University of Texas Southwestern Medical Center, Dallas, TX, United States
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Xiang DF, Thoden JB, Ghosh MK, Holden HM, Raushel FM. Reaction Mechanism and Three-Dimensional Structure of GDP-d-glycero-α-d-manno-heptose 4,6-Dehydratase from Campylobacter jejuni. Biochemistry 2022; 61:1313-1322. [PMID: 35715226 DOI: 10.1021/acs.biochem.2c00244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Campylobacter jejuni is a human pathogen and a leading cause of food poisoning in the United States and Europe. Surrounding the outside of the bacterium is a carbohydrate coat known as the capsular polysaccharide. Various strains of C. jejuni have different sequences of unusual sugars and an assortment of decorations. Many of the serotypes have heptoses with differing stereochemical arrangements at C2 through C6. One of the many common modifications is a 6-deoxy-heptose that is formed by dehydration of GDP-d-glycero-α-d-manno-heptose to GDP-6-deoxy-4-keto-d-lyxo-heptose via the action of the enzyme GDP-d-glycero-α-d-manno-heptose 4,6-dehydratase. Herein, we report the biochemical and structural characterization of this enzyme from C. jejuni 81-176 (serotype HS:23/36). The enzyme was purified to homogeneity, and its three-dimensional structure was determined to a resolution of 2.1 Å. Kinetic analyses suggest that the reaction mechanism proceeds through the formation of a 4-keto intermediate followed by the loss of water from C5/C6. Based on the three-dimensional structure, it is proposed that oxidation of C4 is assisted by proton transfer from the hydroxyl group to the phenolate of Tyr-159 and hydride transfer to the tightly bound NAD+ in the active site. Elimination of water at C5/C6 is most likely assisted by abstraction of the proton at C5 by Glu-136 and subsequent proton transfer to the hydroxyl at C6 via Ser-134 and Tyr-159. A bioinformatic analysis identified 19 additional 4,6-dehydratases from serotyped strains of C. jejuni that are 89-98% identical in the amino acid sequence, indicating that each of these strains should contain a 6-deoxy-heptose within their capsular polysaccharides.
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Affiliation(s)
- Dao Feng Xiang
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - James B Thoden
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Manas K Ghosh
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Hazel M Holden
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Frank M Raushel
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.,Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843, United States
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