Fibrinogenolytic proteases isolated from the snake venom of Taiwan habu: Serine proteases with kallikrein-like and angiotensin-degrading activities

Two venom proteases with fibrinogenolytic activity were isolated from the v enom of Taiwan habu (Trimeresurus mucrosquamatus), one major crotalid snake species in Taiwan. The purified enzymes showed a strong beta -fibrinogenol ytic activity, cleaving beta -chain of fibrinogen molecules specifically Th ey also showed strong kallikrein-like activity in vitro, releasing bradykin in from kininogen. The purified enzymes did not coagulate human plasma, yet decreasing fibrinogen levels in plasma and prolonging bleeding without for mation of fibrin clots, indicating that both proteases have specificities d ifferent from thrombin and thrombin-like proteases of snake venom reported previously. They also exhibit amidase activity against N-benzoyl-Pro-Phe-Ar g-p-nitroanilide, which is a specific synthetic substrate for kallikrein-li ke proteases. Their stability at high temperatures was examined and found t o be more stable when compared with ancrod and thrombin. Intravenous inject ion of either protease was shown to lower blood pressure in experimental ra ts. Most noteworthy is the observation that the proteases can cleave angiot ensin I and release bradykinin from plasma kininogen in vitro, which is a s trong vasodilator and probably responsible for the in vivo hypotensive effe ct of these venom proteases. (C) 2001 Academic Press.