Effect of uridine diphospho-N-acetylglucosamine and sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase activity from rat gastric mucosa.
Mechanisms of inhibitory action of sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase, prepared from rat gastric mucosa, were studied. Sodium salicylate at lower concentrations (10-20 mM) inhibited reversibly aminotransferase activity by competing with fructose-6-phosphate. At higher concentrations, sodium salicylate inactivated the enzyme irreversibly, with an inactivation rate following first-order kinetics with respect to the enzyme concentration. Uridine-5'-diphospho-N-acetylglucosamine is an endogenous feedback inhibitor. It inhibited the aminotransferase-catalyzed reaction also by competing with fructose-6-phosphate but with an inhibiting activity 1000 times that of sodium salicylate. Uridine-5'-diphospho-N-acetylglucosamine reduced the salicylate inhibition of the enzymic reaction and protected the enzyme from salicylate-induced irreversible inactivation. At a fixed concentration of uridine-5'-diphospho-N-acetylglucosamine (7x10(-6)M), an increase of salicylate concentration produced an increase in enzyme activity as compared with the control.
D000818:Animals; D004347:Drug Interactions; D005636:Fructosephosphates; D005753:Gastric Mucosa / Q000201:enzymology*; D005973:Glutamine; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D012459:Salicylates / Q000494:pharmacology*; D013997:Time Factors; D000637:Transaminases / Q000037:antagonists & inhibitors*; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000494:pharmacology*; D014539:Uridine Diphosphate Sugars / Q000494:pharmacology*
D005636:Fructosephosphates; D012459:Salicylates; D014539:Uridine Diphosphate Sugars; D005973:Glutamine; D014537:Uridine Diphosphate N-Acetylglucosamine; D000637:Transaminases