Arginase-1 (Arg-1) is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of arginine to ornithine and urea. It is expressed in normal human liver with a high degree of specificity, concentrated in periportal hepatocytes. Arginase-1 are urea cycle enzymes used to distinguish hepatocellular carcinoma from other carcinomas. Two transcript variants encoding different isoforms have been found for this gene. Inherited deficiency of this enzyme results in argininemia, an autosomal recessive disorder characterized by hyperammonemia.