Inhibition of arginase activity

Patent Granted Arginase's active site is extraordinarily specific. Modifying the substrate structure and/or stereochemistry severely lowers the kinetic activity of the enzyme. This specificity occurs due to the high number of hydrogen bonds between substrate and enzyme; direct or water-facilitated hydrogen bonds exist, saturating both the four acceptor positions on the alpha carboxylate group and all three positions on the alpha amino group. N-hydroxy-L-arginine (NOHA), an intermediate of NO biosynthesis, is a moderate inhibitor of arginase. Crystal structure of its complex with the enzyme reveals that it displaces the metal-bridging hydroxide ion and bridges the binuclear manganese cluster.[6] Additionally, 2(S)-amino-6-boronohexonic acid (ABH) is an L-arginine analogue that also creates a tetrahedral intermediate similar to that formed in the catalysis of the natural substrate, and is a potent inhibitor of human arginase I.