The importance of L-arginine binding to NAGS for normal ureagenesis was confirmed by the case of a hyperammonemic patient found to have a E360D substitution in NAGS; this mutated protein neither binds nor is activated by L-arginine, suggesting that inability to bind L-arginine impairs the function of human NAGS, leading to decreased ureagenesis and hyperammonemia. This evidence concerns the gene NAGS and Hyperammonemia.