Carbamylphosphate hydrolysis in donkey liver.

Mitochondria, microsomes, and cytosol all hydrolyze carbamylphosphate. Microsomes show the greatest specific activity. The mitochondrial enzyme is localized in the inner membranes, has optimum pH 5.5 and is heat-stable; the cytosol enzyme has optimum pH 5.0 and is heat-labile. Km for carbamylphosphate is 1.1 to 1.2 X 10(-2 M for both the cytosol and the mitochondrial enzyme. Both enzymes are inhibited by high substrate concentrations.