title: Enzymatic formation of UDP-N-acetylgalactosamine in epiphysial-plate cartilage.
abstract: The activity of UDP-N-acetylglucosamine 4'-epimerase (EC 5.1.3.7) from newborn pig epiphysial-plate cartilage was investigated. The formation of radioactive UDP-N-acetylgalactosamine from UDP-N-acetyl[U-14C]-glucosamine was demonstrated by radioautography, after hydrolysis of UDP-derivatives and separation of the hexosamines by paper chromatography. The pH optimum and the Km values for UDP-N-acetylglucosamine and NAD were determined. At equilibrium, the ratio UDP-N-acetylglucosamine/UDP-N-acetylgalactosamine reaches a value of about 2.3. The effect of UDP-xylose and UDP-glucuronic acid on the enzyme activity was investigated. NADH inhibits UDP-N-acetylglucosamine 4'-epimerase activity. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH.
mesh_terms: D000818:Animals; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D002356:Cartilage / Q000201:enzymology*; D004838:Epiphyses; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009243:NAD / Q000494:pharmacology; D013552:Swine; D014535:Uridine Diphosphate Glucuronic Acid / Q000494:pharmacology; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000096:biosynthesis; D014540:Uridine Diphosphate Xylose / Q000494:pharmacology
chemical_list: D009243:NAD; D014535:Uridine Diphosphate Glucuronic Acid; D014540:Uridine Diphosphate Xylose; D014537:Uridine Diphosphate N-Acetylglucosamine; D002238:Carbohydrate Epimerases