@article {2510,
	title = {The Engineering of Bacteria Bearing Azido-Pseudaminic Acid-Modified Flagella},
	journal = {Chembiochem},
	volume = {10},
	number = {8},
	year = {2009},
	note = {ISI Document Delivery No.: 452SMTimes Cited: 3Cited Reference Count: 24Liu, Feng Aubry, Annie J. Schoenhofen, Ian C. Logan, Susan M. Tanner, Martin E.},
	month = {May},
	pages = {1317-1320},
	type = {Article},
	keywords = {4, 6-DEHYDRATASE, azides, biosynthesis, C. jejuni, CAMPYLOBACTER-JEJUNI, cell surfaces, flagella, FUNCTIONAL-CHARACTERIZATION, HELICOBACTER-PYLORI, IDENTIFICATION, METABOLISM, PATHWAY, PROTEINS, PseB, reaction, Staudinger, UDP-N-ACETYLGLUCOSAMINE},
	isbn = {1439-4227},
	url = {<Go to ISI>://000266561500009},
	author = {Liu, F. and Aubry, A. J. and Schoenhofen, I. C. and Logan, S. M. and Tanner, M. E.}
}
@article {2140,
	title = {Mechanism and Active Site Residues of GDP-Fucose Synthase},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {51},
	year = {2008},
	note = {ISI Document Delivery No.: 406UOTimes Cited: 3Cited Reference Count: 37Lau, Stephen T. B. Tanner, Martin E.},
	month = {Dec},
	pages = {17593-17602},
	type = {Article},
	abstract = {L-Fucose, 6-deoxy-L-galactose, is a key component of many important glycoconjugates including the blood group antigens and the Lewis(x) ligands. The biosynthesis of GDP-L-fucose begins with the action of a dehydratase that converts GDP-D-mannose into GDP-4-keto-6-deoxy-mannose. The enzyme GDPfucose synthase, GFS, (also known as GDP-4-keto-6-deoxy-D-mannose epimerase/reductase, GMER) then converts GDP-4-keto-6-deoxy-D-mannose into GDP-L-fucose. The GFS reaction involves epimerizations at both C-3 {\textquoteright}{\textquoteright} and C-5 {\textquoteright}{\textquoteright} followed by an NADPH-dependent reduction of the carbonyl at C-4. This manuscript describes studies that elucidate the order of the epimerization steps and the roles of the active site acid/base residues responsible for the epimerizations. An active site mutant, Cys109Ser, produces GDP-6-deoxy-D-altrose as its major product indicating that C-3 {\textquoteright}{\textquoteright} epimerization occurs first and premature reduction of the GDP-4-keto-6-deoxy-D-altrose intermediate becomes competitive with GDP-L-fucose production. The same mutation results in the appearance of a kinetic isotope effect when [3 {\textquoteright}{\textquoteright}-H-2]-GDP-6-deoxy-4-keto-mannose is used as a substrate. This indicates that Cys109 is the base responsible for the deprotonation of the substrate at C-3 {\textquoteright}{\textquoteright}. The Cys109Ser mutant also catalyzes a rapid wash-in of solvent derived deuterium into the C-5 {\textquoteright}{\textquoteright} position of GDP-fucose in the presence of NADP(+). This confirms the order of epimerizations and the role of Cys109. Finally, the inactive His179Gln mutant readily catalyzes the wash-out of deuterium from the C-3 {\textquoteright}{\textquoteright} position of [3 {\textquoteright}{\textquoteright}-H-2]-GDP-6-deoxy-4-keto-mannose. Together these results strongly implicate an ordered sequence of epimerizations (C-3 {\textquoteright}{\textquoteright} followed by C-5 {\textquoteright}{\textquoteright}) and suggest that Cys109 acts as a base and His179 acts as an acid in both epimerization steps.},
	keywords = {6-DEHYDRATASE, ARABIDOPSIS-THALIANA, BIOLOGICAL FUNCTION, CATALYTIC MECHANISM, DTDP-GLUCOSE 4, ESCHERICHIA-COLI, GDP-4-KETO-6-DEOXY-D-MANNOSE EPIMERASE/REDUCTASE, HELICOBACTER-PYLORI, LEUKOCYTE ADHESION, MANNOSE 4, UDP-GALACTOSE 4-EPIMERASE},
	isbn = {0002-7863},
	url = {<Go to ISI>://000263320600076},
	author = {Lau, S. T. B. and Tanner, M. E.}
}
@article {2193,
	title = {Mechanistic studies on PseB of pseudaminic acid biosynthesis: A UDP-N-acetylglucosamine 5-inverting 4,6-dehydratase},
	journal = {Bioorganic Chemistry},
	volume = {36},
	number = {4-6},
	year = {2008},
	note = {ISI Document Delivery No.: 386TPTimes Cited: 2Cited Reference Count: 33Morrison, James P. Schoenhofen, Ian C. Tanner, Martin E.},
	month = {Aug-Dec},
	pages = {312-320},
	type = {Article},
	abstract = {UDP-N-acetylglucosamine 5-inverting 4,6-dehydratase (PseB) is a unique sugar nucleotide dehydratase that inverts the C-5 {\textquoteright}{\textquoteright} stereocentre during conversion of UDP-N-acetylglucosamine to UDP-2-acetamido2,6-dideoxy-beta-L-arabino-hexos-4-ulose. PseB catalyzes the first step in the biosynthesis of pseudaminic acid, which is found as a post-translational modification on the flagellin of Campylobacter jejuni and Helicobacter pylori. PseB is proposed to use its tightly bound NADP(+) to oxidize UDP-GlcNAc at C-4 {\textquoteright}{\textquoteright}, enabling dehydration. The alpha,beta unsaturated ketone intermediate is then reduced by delivery of the hydride to C-6 {\textquoteright}{\textquoteright} and a proton to C-5 {\textquoteright}{\textquoteright}. Consistent with this, PseB from C. jejuni has been found to incorporate deuterium into the C-5 {\textquoteright}{\textquoteright} position of product during catalysis in D2O. Likewise, PseB catalyzes solvent isotope exchange into the H-5 {\textquoteright}{\textquoteright} position of product, and eliminates HF from the alternate Substrate, UDP-6-deoxy-6-fluoro-GlcNAc. Mutants of the putative catalytic residues aspartate 126, lysine 127 and tyrosine 135 have severely compromised dehydratase, solvent isotope exchange, and HF elimination activities. (C) 2008 Elsevier Inc. All rights reserved.},
	keywords = {6-DEHYDRATASE, Campylobacter jejuni, CAMPYLOBACTER-JEJUNI, dehydratase, DTDP-GLUCOSE 4, ENZYMES, FLAA1, FUNCTIONAL-CHARACTERIZATION, GDP-MANNOSE 4, HELICOBACTER-PYLORI, IDENTIFICATION, Inverting, MOTILITY, PATHWAY, PseB, Pseudaminic acid, UDP-N-acetylglucosamine 5-inverting 4},
	isbn = {0045-2068},
	url = {<Go to ISI>://000261905800019},
	author = {Morrison, J. P. and Schoenhofen, I. C. and Tanner, M. E.}
}
@article {1464,
	title = {PseG of pseudaminic acid biosynthesis - A UDP-sugar hydrolase as a masked glycosyltransferase},
	journal = {Journal of Biological Chemistry},
	volume = {281},
	number = {30},
	year = {2006},
	note = {ISI Document Delivery No.: 065VFTimes Cited: 12Cited Reference Count: 40Liu, Feng Tanner, Martin E.},
	month = {Jul},
	pages = {20902-20909},
	type = {Article},
	abstract = {The flagellin proteins in pathogenic bacteria such as Campylobacter jejuni and Helicobacter pylori are heavily glycosylated with the nine-carbon alpha-keto acid, pseudaminic acid. The presence of this posttranslational modification is absolutely required for assembly of functional flagella. Since motility is required for colonization, pseudaminic acid biosynthesis represents a virulence factor in these bacteria. Pseudaminic acid is generated from UDP-N-acetylglucosamine in five biosynthetic steps. The final step has been shown to involve the condensation of 2,4-diacetamido- 2,4,6-trideoxy-L-altrose ( 6-deoxy-AltdiNAc) with phosphoenolpyruvate as catalyzed by the enzyme pseudaminic acid synthase, NeuB3. The 6-deoxy-AltdiNAc used in this process is generated from its nucleotide-linked form, UDP-6-deoxy-AltdiNAc, by the action of a hydrolase that cleaves the glycosidic bond and releases UDP. This manuscript describes the first characterization of a UDP-6-deoxy-AltdiNAc hydrolase, namely PseG ( Cj1312) from C. jejuni. The activity of this enzyme is independent of the presence of divalent metal ions, and the values of the catalytic constants were found to be k(cat) = 27 s(-1) and K-m = 174 mu M. The enzyme was shown to hydrolyze the substrate with an overall inversion of stereochemistry at C-1 and to utilize a C-O bond cleavage mechanism during catalysis. These results, coupled with homology comparisons, suggest that the closest ancestors to the hydrolase are members of the metal-independent GT-B family of glycosyltransferases that include the enzyme MurG.},
	keywords = {CAMPYLOBACTER-JEJUNI, FLAGELLIN, FUNCTIONAL-CHARACTERIZATION, GLYCOPROTEINS, glycosylation, HELICOBACTER-PYLORI, IDENTIFICATION, MECHANISM, N-ACETYLGLUCOSAMINE 2-EPIMERASE, NUDIX HYDROLASES, SYNTHASE},
	isbn = {0021-9258},
	url = {<Go to ISI>://000239187300027},
	author = {Liu, F. and Tanner, M. E.}
}
@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.}
}
