Arginase I (also designated liver-type arginase), which is expressed almost exclusively in the liver, catalyzes the conversion of arginine to ornithine and urea. Mammalian arginase is active as a trimer, but some bacterial arginases are hexameric. Arginase1 is activated by lactic acid in tumors to stimulate macrophages to help a tumor grow. When arginase1 was inhibited in a mouse model tumor size was greatly reduced. In addition, research studies have demonstrated that Arginase-1 distinguishes primary hepatocellular carcinoma (HCC) from metastatic tumors in the liver, indicating its value as a potential biomarker in the diagnosis of HCC.
