title: New UDP-GlcNAc C4 epimerase involved in the biosynthesis of 2-acetamino-2-deoxy-L-altruronic acid in the O-antigen repeating units of Plesiomonas shigelloides O17.
abstract: Plesiomonas shigelloides is a ubiquitous waterborne pathogen responsible for diseases such as diarrhea and bacillary dysentery, commonly afflicting infants and children. This bacterium is endowed with an O-antigen gene cluster consisting of 10 consecutive reading frames. One of these, designated wbgU (orf3), has been overexpressed and biochemically characterized to show that it encodes a uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) C4 epimerase, only the second microbial enzyme characterized to have this activity. Epimerization is an equilibrium reaction resulting in a 70:30 ratio of UDP-GlcNAc to uridine diphosphate-N-acetylgalactosamine (UDP-GalNAc), irrespective of the initial substrate. The K(m) values for UDP-GalNAc and UDP-GlcNAc are 131 microM and 137 microM, respectively. WbgU is also capable of converting nonacetylated derivatives but with much lower efficiency. It contains a tightly bound nicotinamide adenine dinucleotide [NAD(H)] molecule and requires no other cofactors for activity. We propose here that this enzyme catalyzes the first of the three transformations in the biosynthetic pathway of 2-acetamino-2-deoxy-L-altruronic acid, an unusual sugar present in the O-specific side chains of lipopolysaccharide of P. shigelloides O17 and its close relative Escherichia coli Sonnei.
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Kowal
authors.forename: Peng George
authors.initials: PG
authors.lastname: Wang
mesh_terms: D002238:Carbohydrate Epimerases / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D019075:Electrophoresis, Capillary; D004789:Enzyme Activation; D007700:Kinetics; D008070:Lipopolysaccharides / Q000096:biosynthesis; D009243:NAD / Q000737:chemistry / Q000302:isolation & purification; D019081:O Antigens / Q000096:biosynthesis*; D009844:Oligosaccharides / Q000096:biosynthesis; D016981:Plesiomonas / Q000201:enzymology* / Q000235:genetics; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D013379:Substrate Specificity; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000031:analogs & derivatives* / Q000737:chemistry; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000737:chemistry; D014574:Uronic Acids / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; D019081:O Antigens; D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; D011994:Recombinant Proteins; D014574:Uronic Acids; D009243:NAD; C051472:uridine diphosphate galactosamine; D014537:Uridine Diphosphate N-Acetylglucosamine; D014536:Uridine Diphosphate N-Acetylgalactosamine; C102528:altruronic acid; D002238:Carbohydrate Epimerases; C023223:UDP-N-acetylglucosamine 4-epimerase