The ARG1 gene encodes arginase enzyme. This enzyme catalyzes the last step of the urea cycle, which is one of the metabolic pathways in the liver, where arginase is cytoplasmic. The metabolism of proteins in the diet creates nitrogen, as a waste product, in the circulatory system. The urea cycle processes this nitrogen, in the form of ammonia, from the blood, through a sequence of biochemical processes. Arginase is responsible for the incorporation of ammonia into urea, which can then be excreted from the body in urine. If urea cannot be synthesized, nitrogen accumulates in the blood and body tissues, as ammonia, which is a highly toxic substance, and may lead to brain damage and /or death. Arginase is also the enzyme necessary to regenerate the starting compound in the urea cycle, converting arginine to ornithine and beginning the cycle again.