CHEMISTRY AND BIOCHEMISTRY OF KALLIKREIN-LIKE ENZYME FROM SNAKE-VENOMS

The chemical and physiological properties of various kallikrein-like ( kinin-releasing) enzymes from Viperidae and Crotalidae snake venoms ha ve been compared. These enzymes act on plasma kininogen to release the potent vasodepressors bradykinin and/or kallidin. Moreover, they hydr olyze the vasopressor angiotensin II and its precursor angiotensin I. Although fibrinogen clotting ability is absent from kallikrein-like en zymes, most of these enzymes degrade the peptide chains of fibrinogen. Considerable sequence homology occurs between kallikrein-like enzymes and thrombin-like enzymes, however physiological substrate specificit ies of the two enzymes differ. Similarities and differences in the str ucture and function of these enzymes is discussed.