Arginase

Arginase is one of the several enzymes thatmetabolize the semi-essential amino acid,L-arginine. The other enzymes which metabolizeL-arginine include:1. Nitric oxide synthase (NO production).2. Arginyl-tRNA synthetase (protein produ ction).3. Arginine:glycine aminotransferase (creatineproduction).4. Arginine decarboxylase (agmatine produ ction).Of special note is the competitionbetween arginase and nitric oxide synthase(NOS) for L-arginine. This has been a growingfocal point for biomedical research inrecent years, because a change in the balancecan vastly affect cellular function.Arginase is distributed in tissue throughoutthe body in two isoforms and has functionsin both health and disease. Arginase convertsL-arginine into urea and ornithine - in manytissues ornithine can be further metabolized topolyamines, proline and glutamate. Theseproducts have important biological functions.Arginase function in the liver is extremelyimportant. It is part of a cycle which releasesurea and produces ornithine, which thenaccepts hepatic metabolites of NH3 in the productionof citrulline, the precursor of L-arginine.This hepatic urea cycle is essential for riddingthe body of toxic NH3 via the release of urea.Arginase also is beneficial in wound healingand neuroprotection/regeneration. Arginasealso has key functions in a number of diseasestates. These prominently include vascular andendothelial dysfunctions associated with diabetes,hypertension, sickle cell disease, ischaemia/reperfusion injury, atherosclerosis anderectile dysfunction. Other diseases involvingelevated arginase activity are asthma, nephropathy,cancer, and parasitic infections.Stimuli that increase arginase activity/expression include reactive oxygen species,inflammatory cytokines and humoral factors,including angiotensin II and thrombin. Studiesof signal transduction mechanisms and developmentof inhibitors of the activation processesare under way with the goal of limitingarginase function to physiological levels.