Metabolism of Kinins

METABOLISM OF KININS

Kinins are metabolized rapidly (half-life < 15 seconds) by nonspe-cific exopeptidases or endopeptidases, commonly referred to as kininases. Two plasma kininases have been well characterized. Kininase I, apparently synthesized in the liver, is a carboxypepti-dase that releases the carboxyl terminal arginine residue. Kininase is present in plasma and vascular endothelial cells throughout the body. It is identical to angiotensin-converting enzyme (ACE, peptidyl dipeptidase), discussed above. Kininase II inactivateskinins by cleaving the carboxyl terminal dipeptide phenylalanyl-arginine. Like angiotensin I, bradykinin is almost completely hydrolyzed during a single passage through the pulmonary vascular bed.