. "Arginase is an enzyme catalyzing the hydrolysis of arginine to form ornithine and urea through a metal-activated hydroxide mechanism |CITS: [11258880]|. In mammals two isozymes of arginase are recognized: A cytosolic form, |FRAME: CPLX-6621| (AI), is highly expressed in the liver and is thought to be primarily involved in ureagenesis, and a mitochondrial form, |FRAME: CPLX-6622| (AII), was reported to be widely expressed and to be involved in the biosynthesis of polyamines, the amino acids ornithine, proline, and glutamate, and in the inflammatory process, among others. A more recent work, using in situ and quantitative PCR studies in mouse, reported that AI and not AII is the predominant isoform expressed during development and in the majority of organs |CITS: [15050972]|. While AI knockout mice die at the age of 10-12 days |CITS: [12052859]|, the only phenotype of an AII knockout mouse was diminished fertility in homozygous males, supporting the observation that AII, which is highly expressed in prostate, is important for sperm function in semen |CITS: [11154268] [15050972]|. Human |FRAME: CPLX-6621| is an important member of the urea cycle, and functions in the net production of urea for excretion of excess nitrogen. It is abundant in the liver of ureotelic animals (animals that excrete urate as the chief end-product of nitrogen metabolism). The human enzyme exists most likely as a trimer |CITS: [11370664][2515788]| although there has been a claim that it exists as a monomer in its natural form |CITS: [2241902]|."^^ . . . . . "arginase type 1"^^ . "liver-type arginase"^^ . "arginase type 1"^^ . .