ARG1 is a member of the ureohydrolase family of enzymes. ARG1 can catalyze the hydrolysis of arginine to ornithine and urea. In the urea cycle, ARG1 catalyzes the fifth and final step, a series of biochemical reactions in mammals during which the body disposes of harmful ammonia. ARG1 is a cytosolic enzyme and expressed widely in the liver as part of the urea cycle, while it is also expressed in cells and tissues that lack a complete urea cycle, including lung. Inherited deficiency of this ARG1 causes argininemia, which is an autosomal recessive disorder characterized by hyperammonemia.