@article {1084,
	title = {Identification and characterization of NeuB3 from Campylobacter jejuni as a pseudaminic acid synthase},
	journal = {Journal of Biological Chemistry},
	volume = {280},
	number = {43},
	year = {2005},
	note = {ISI Document Delivery No.: 976IMTimes Cited: 22Cited Reference Count: 43},
	month = {Oct},
	pages = {35922-35928},
	type = {Article},
	abstract = {Campylobacter jejuni and Campylobacter coli are the main causes of bacterial diarrhea worldwide, and Helicobacter pylori is known to cause duodenal ulcers. In all of these pathogenic organisms, the flagellin proteins are heavily glycosylated with a 2-keto-3-deoxy acid, pseudaminic acid (5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L- manno-nonulosonic acid). The presence of pseudaminic acid is required for the proper development of the flagella and is thereby necessary for motility in, and invasion of, the host. In this study we report the first characterization of NeuB3 from C. jejuni as a pseudaminic acid synthase; the enzyme directly responsible for the biosynthesis of pseudaminic acid. Pseudaminic acid synthase catalyzes the condensation of phosphoenolpyruvate ( PEP) with the hexose, 2,4-diacetamido-2,4,6- trideoxy-L-altrose (6-deoxy-AltdiNAc), to form pseudaminic acid and phosphate. The enzymatic activity was monitored using H-1 and P-31 NMR spectroscopy, and the product was isolated and characterized. Kinetic analysis reveals that pseudaminic acid synthase requires the presence of a divalent metal ion for catalysis and that optimal catalysis occurs at pH 7.0. A coupled enzymatic assay gave the values for k(cat) of 0.65 +/- 0.01 s(-1), KmPEP of 6.5 +/- 0.4 mu M, and K(m)6-deoxy- AltdiNAc of 9.5 +/- 0.7 mu M. A mechanistic study on pseudaminic acid synthase, using[2-O-18] PEP, shows that catalysis proceeds through a C-O bond cleavage mechanism similar to other PEP condensing synthases such as sialic acid synthase.},
	keywords = {BISUBSTRATE INHIBITOR, ESCHERICHIA-COLI, HELICOBACTER-PYLORI, KDO8P SYNTHASE, NEISSERIA-MENINGITIDIS, O-SPECIFIC POLYSACCHARIDE, PNEUMOPHILA SEROGROUP-1 LIPOPOLYSACCHARIDE, PSEUDOMONAS-AERUGINOSA, SIALIC ACIDS, SOMATIC ANTIGENS},
	isbn = {0021-9258},
	url = {<Go to ISI>://000232726900019},
	author = {Chou, W. K. and Dick, S. and Wakarchuk, W. W. and Tanner, M. E.}
}
@article {859,
	title = {Active site residues and mechanism of UDP-glucose dehydrogenase},
	journal = {European Journal of Biochemistry},
	volume = {271},
	number = {1},
	year = {2004},
	note = {ISI Document Delivery No.: 756CXTimes Cited: 16Cited Reference Count: 33},
	month = {Jan},
	pages = {14-22},
	type = {Article},
	abstract = {UDP-glucose dehydrogenase catalyzes the NAD(+)-dependent twofold oxidation of UDP-glucose to give UDP-glucuronic acid. A sequestered aldehyde intermediate is produced in the first oxidation step and a covalently bound thioester is produced in the second oxidation step. This work demonstrates that the Streptococcus pyogenes enzyme incorporates a single solvent-derived oxygen atom during catalysis and probably does not generate an imine intermediate. The reaction of UDP-[6",6"-di-H-2]-D-glucose is not accompanied by a primary kinetic isotope effect, indicating that hydride transfer is not rate determining in this reaction. Studies with a mutant of the key active site nucleophile, Cys260Ala, show that it is capable of both reducing the aldehyde intermediate, and oxidizing the hydrated form of the aldehyde intermediate but is incapable of oxidizing UDP-glucose to UDP-glucuronic acid. In the latter case, a ternary Cys260Ala/aldehyde intermediate/NADH complex is presumably formed, but it does not proceed to product as both release and hydration of the bound aldehyde occur slowly. A washout experiment demonstrates that the NADH in this ternary complex is not exchangeable with external NADH, indicating that dissociation only occurs after the addition of a nucleophile to the aldehyde carbonyl. Studies on Thr118Ala show that the value of k(cat) is reduced 160-fold by this mutation, and that the reaction of UDP-D-[6",6"-di-H-2]-glucose is now accompanied by a primary kinetic isotope effect. This indicates that the barriers for the hydride transfer steps have been selectively increased and supports a mechanism in which an ordered water molecule (H-bonded to Thr118) serves as the catalytic base in these steps.},
	keywords = {ACID, ALDEHYDE DEHYDROGENASE, CONSERVED CYSTEINE RESIDUES, DEHYDROGENASE, ENZYME, GDP-MANNOSE DEHYDROGENASE, GROUP-A STREPTOCOCCI, HISTIDINOL, MOLECULAR CHARACTERIZATION, PSEUDOMONAS-AERUGINOSA, URIDINE DIPHOSPHOGLUCOSE DEHYDROGENASE},
	isbn = {0014-2956},
	url = {<Go to ISI>://000187449200002},
	author = {Ge, X. and Penney, L. C. and van de Rijn, I. and Tanner, M. E.}
}
