Arginase catalyzes the fifth and final step in the urea cycle, a series of biochemical reactions in mammals during which the body disposes of harmful ammonia.

[4] In most mammals, two isozymes of this enzyme exist; the first, Arginase I, functions in the urea cycle, and is located primarily in the cytoplasm of hepatocytes (liver cells).

[citation needed] 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.

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.

Due to this alternate method of removing excess arginine and ammonia from the bloodstream, subjects with arginase deficiency tend to have longer lifespans than those who have other urea cycle defects.

While some symptoms of the disease can be controlled via dietary restrictions and pharmaceutical developments, no cure or completely effective therapy currently exists.