title: Inhibition of carbamoyl-phosphate synthase (ammonia) by Tris and Hepes. Effect on Ka for N-acetylglutamate.
abstract: The apparent Ka for N-acetylglutamate of rat liver carbamoyl-phosphate synthase is 11 microM in phosphate buffer, a value 10-fold lower than reported in other buffer systems. Tris and Hepes inhibit competitively with N-acetylglutamate. The proportion of carbamoyl-phosphate synthase in the active enzyme-acetylglutamate complex in vivo may be higher than previous calculations suggest, which re-opens the question of the involvement of N-acetylglutamate in the regulation of urea synthesis.
mesh_terms: D000818:Animals; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000037:antagonists & inhibitors*; D002956:Citrulline / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D006531:HEPES / Q000494:pharmacology*; D007700:Kinetics; D008025:Ligases / Q000037:antagonists & inhibitors*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology; D009840:Oligomycins / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D051381:Rats; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D005971:Glutamates; D009840:Oligomycins; D010879:Piperazines; D014325:Tromethamine; D002956:Citrulline; D008025:Ligases; D002222:Carbamoyl-Phosphate Synthase (Ammonia); C016195:N-acetylglutamic acid; D006531:HEPES