Arginase [EC 18.104.22.168; L-arginine aminohydrolase] is an enzyme that hydrolyzes Larginine to L-ornithine and urea in the urea cycle. Two forms of arginase exists which are designed as arginase I and arginase II. Liver-type arginase I is expressed primarily in the liver and to some extend in the erythrocytes. Arginase II is expressed in many extrahepatic tissues, such as brain, spinal cord, kidney, small intestine and mammary gland. Although arginase I and arginase II have similar enzyme activities, they have different pI, immunological reactivity and are encoded by different genes. Human arginase I is a 35 kDa protein circulating in blood probably as a homotrimer. Circulating liver-type arginase was clinically used as a liver specific marker which may reflect not only early occurrence of liver injury but also early termination of liver injury. The measurement of liver-type arginase is clinically applicable for monitoring conditions of patients with liver disorders or pre- and postoperative conditions of patients who received partial hepatectomy with quicker normalization in comparison with aminotransferases (ALT and AST). Recently, arginase I gene was found to be one of the most prominent among astma genes. In situ hybridization demonstrated marked staining of arginase I in submucosal inflammatory lesions and arginase activity increased in allergen challenged lungs. Finally, it was found that both arginase I was the most significantly up-regulated protein in the murine spinal cord during experimental autoimmune encephalomyelitis. The results indicated that arginase I played important roles in autoimmune inflammation in the central nervous system.
- References to Arginase I (EC 22.214.171.124, L-arginine aminohydrolase)