ARG1 catalyzes the hydrolysis of arginine to ornithine and urea. 2 isoforms of mammalian arginase exist which vary in their tissue distribution, subcellular localization, immunologic crossreactivity and physiologic role. ARG1 is a cytosolic enzyme and expressed widely in the liver as part of the urea cycle. Inherited deficiency of this ARG1 causes argininemia, which is an autosomal recessive disorder characterized by hyperammonemia.