@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.}
}
@article {3922,
	title = {Properties and kinetic analysis of UDP-glucose dehydrogenase from group a streptococci - Irreversible inhibition by UDP-chloroacetol},
	journal = {Journal of Biological Chemistry},
	volume = {272},
	number = {6},
	year = {1997},
	note = {ISI Document Delivery No.: WG192Times Cited: 39Cited Reference Count: 48},
	month = {Feb},
	pages = {3416-3422},
	type = {Article},
	abstract = {UDP-glucuronic acid is used by many pathogenic bacteria in the construction of an antiphagocytic capsule that is required for virulence. The enzyme UDP-glucose dehydrogenase catalyzes the NAD(+)-dependent 2-fold oxidation of UDP-glucose and provides a source of the acid. In the present study the recombinant dehydrogenase from group A streptococci has been purified and found to be active as a monomer. The enzyme contains no chromophoric cofactors, and its activity is unaffected by the presence of EDTA or carbonyl-trapping reagents. Initial velocity and product inhibition kinetic patterns are consistent with a bi-uni-uni-bi ping-pong mechanism in which UDP-glucose is bound first and UDP-glucuronate is released last. UDP-xylose was found to be a competitive inhibitor (K-i, 2.7 mu M) of the enzyme. The enzyme is irreversibly inactivated by uridine 5{\textquoteright}-diphosphate chloroacetol due to the alkylation of an active site cysteine thiol. The apparent second order rate constant for the inhibition (k(i)/K-i) was found to be 2 x 10(3) mM(-1) min(-1). Incubation with the truncated compound, chloroacetol phosphate, resulted in no detectable inactivation when tested under comparable conditions. This supports the notion that uridine 5{\textquoteright}-diphosphate-chloroacetol is bound in the place of UDP-glucose and is not simply acting as a nonspecific alkylating agent.},
	keywords = {ALDEHYDE DEHYDROGENASE, BOVINE LIVER, CAPSULE, CONSERVED CYSTEINE RESIDUES, GROUP-A STREPTOCOCCI, HISTIDINOL DEHYDROGENASE, HYALURONIC-ACID SYNTHESIS, MOLECULAR CHARACTERIZATION, MUTAGENESIS, PNEUMONIAE, SITE-DIRECTED},
	isbn = {0021-9258},
	url = {<Go to ISI>://A1997WG19200045},
	author = {Campbell, R. E. and Sala, R. F. and vandeRijn, I. V. and Tanner, M. E.}
}
