title: Structure-activity studies of glucose transfer: determination of the spontaneous rates of hydrolysis of uridine 5'-diphospho-alpha-D-glucose (UDPG) and uridine 5'-diphospho-alpha-D-glucuronic acid (UDPGA).
abstract: The pH-rate profiles for the hydrolysis of uridine 5'-diphospho-alpha-D-glucose (UDPG) and uridine 5'-diphospho-alpha-D-glucuronic acid (UDPGA) in aqueous solution have been measured. The results obtained and a comparison with other data suggests that the mechanism of hydrolysis of each activated glycosyl-donor at pH 1-4 probably involves the slow ionisation, via an S(N)1 process, of the neutral molecule to a glycosyl ion and UDP. From these data, the catalytic power (k(cat)/k(uncat)) of the glycosyltransferases has been estimated for the first time to be in the order of 10(11-13).
authors.affiliation: School of Biosciences, University of Westminster, 115New Cavendish Street, London W1W 6UW, UK. c.t.bedford@ucl.ac.uk
authors.forename: Colin T
authors.initials: CT
authors.lastname: Bedford
authors.forename: Alan D
authors.initials: AD
authors.lastname: Hickman
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Logan
mesh_terms: D002384:Catalysis; D005947:Glucose / Q000737:chemistry*; D005958:Glucosephosphates / Q000737:chemistry; D016695:Glycosyltransferases / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D013329:Structure-Activity Relationship; D014532:Uridine Diphosphate Glucose / Q000737:chemistry*; D014535:Uridine Diphosphate Glucuronic Acid / Q000737:chemistry*
chemical_list: D005958:Glucosephosphates; D014535:Uridine Diphosphate Glucuronic Acid; D016695:Glycosyltransferases; D005947:Glucose; D014532:Uridine Diphosphate Glucose