Arginase is a manganese-containing metalloenzyme that catalyses the hydrolysis of ʟ-arginine to ʟ-ornithine and urea. Two arginase isoforms coexist: cytosolic type I (Arg1), predominantly expressed in the liver, and primarily involved in ureagenesis, and mitochondrial type II (Arg2), widely expressed in extrahepatic tissues and mainly involved in the production of ʟ-ornithine outside the urea cycle.