Uridine Diphosphate-4-Keto-Glucose an Intermediate in the Uridine Diphosphate-Galactose-4-Epimerase Reaction

摘要

When UDP-galactose 4-epimerase (EC 5.1.3.2) from Escherichia coli is incubated with UDP-galactose, then reduced with NaB³H4, label is found in UDP-glucose and UDP-galactose. Enzymatic and chemical degradation demonstrates that the label is bound to carbon 4 of the glycosyl moieties. These results provide direct evidence for the existence of UDP-4-keto-glucose as an enzyme-bound intermediate in the epimerization reaction, and they exclude the formation of a 3-keto intermediate.