Modulation of the activity of rat liver acetylglutamate synthase by pH and arginine concentration

Acetylglutamate is known to modulate the activity of carbamyl phosphate synthetase, and thus probably to participate in regulation of the urea cycle. Therefore factors that regulate the activity of acetylglutamate synthase are relevant to control of urea synthesis and of systemic pH. An increase in the concentration of arginine increases both Vmax and S0.5 for glutamate of acetylglutamate synthase from rat liver. An increase in pH causes S0.5 for glutamate to decrease and does not affect Vmax. As a consequence of these effects, a rapid rate of synthesis of acetylglutamate requires a concentration of arginine of about 25 microM or higher and either relatively high glutamate concentrations or relatively high pH.