title: Effect of some nucleotides on the regulation of glycosaminoglycan biosynthesis.
abstract: The effect of some nucleotides on UDP-glucose dehydrogenase (EC. 1.1.1.22) and UDP-glucose 4'-epimerase (EC 5.1.3.2) extracted from epiphysial-plate cartilage of newborn pigs was investigated. UDP-xylose acts as a co-operative allosteric inhibitor of UDP-glucose dehydrogenase, whereas it does not inhibit UDP-glucose 4'-epimerase activity: the inhibition of UDP-glucose dehydrogenase results in an increase of UDP-galactose synthesis, in agreement with the equilibrium constant of UDP-glucose 4'-epimerase reaction. Because of the presence of UDP-glucose 4'-epimerase activity in the enzyme extract, the addition of UDP-galactose induces an increase in reaction rate of UDP-glucose dehydrogenase. NADH inhibits both UDP-glucose dehydrogenase and UDP-glucose 4'-epimerase activities: in the presence of non-saturating NAD concentrations, NADH acts as a co-operative allosteric inhibitor of both enzymes. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH. In any case, the percentage inhibition of UDP-glucose 4'-epimerase, under the same experimental conditions, is always higher than that of UDP-glucose dehydrogenase.
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002356:Cartilage / Q000201:enzymology; D004838:Epiphyses / Q000201:enzymology; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D009243:NAD / Q000494:pharmacology; D013552:Swine; D014534:UDPglucose 4-Epimerase / Q000037:antagonists & inhibitors / Q000378:metabolism; D014531:Uridine Diphosphate Galactose / Q000096:biosynthesis / Q000494:pharmacology*; D014532:Uridine Diphosphate Glucose / Q000378:metabolism / Q000494:pharmacology*; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D014535:Uridine Diphosphate Glucuronic Acid; D014539:Uridine Diphosphate Sugars / Q000494:pharmacology*; D014540:Uridine Diphosphate Xylose / Q000494:pharmacology
chemical_list: D006025:Glycosaminoglycans; D014539:Uridine Diphosphate Sugars; D009243:NAD; D014535:Uridine Diphosphate Glucuronic Acid; D014531:Uridine Diphosphate Galactose; D014540:Uridine Diphosphate Xylose; D014533:Uridine Diphosphate Glucose Dehydrogenase; D014534:UDPglucose 4-Epimerase; D014532:Uridine Diphosphate Glucose