Kinetics of inhibition of rat liver and kidney arginases by proline and branched-chain amino acids.

The effects of proline, leucine, isoleucine and valine on kidney and liver arginases were studied. At pH 7.5 and at nearly physiological concentrations, the branched-chain amino acids caused a significant inhibition of liver arginase A1 and only minor effects on kidney arginase A4. Kidney arginase was, however, much more sensitive to inhibition by proline than the liver enzyme. The inhibition of liver and kidney arginases by branched-chain amino acids was partial, indicating the existence of allosteric sites on both enzymes. The function of kidney arginase in proline biosynthesis and a possible role of branched-chain amino acids in the hydrolysis of arginine in liver is discussed.