Comp Biochem Physiol B 1982 Jan 01;732:215-20.

Kinetic properties of arginase from Xenopus laevis.

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1. Arginase from the liver of Xenopus laevis has a Michaelis constant (Km) for arginine of 42 mM, a minor component having a Km of 29 mM. The Km is independent of pH in the range of 7.0-11.0 and also independent of manganese ion concentration. 2. Manganese is required for activation, showing an optimum at 50 mM with inhibition at higher concentrations. 3. The enzyme is inhibited by high concentrations of the substrate L-arginine and by L-lysine and L-ornithine in a competitive manner with respect to arginine. 4. In its Michaelis constant for arginine and inhibition by high substrate concentration, Xenopus liver arginase resembles "ureotelic" arginases.

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