Effects of venom proteases on peptide chromogenic substrates and bovine prothrombin

Eighteen proteases were isolated from six hemorrhagic venoms of snakes belonging to the families of Crotalidae and Viperidae. According to their actions, they are classified as thrombin-like enzymes, alpha-fibrinogenases, beta-fibrinogenases, Factor X activator, prothrombin activator, hemorrhagins and esterases. Thrombin-like enzymes, beta-fibrinogenases, hemorrhagins and esterase hydrolyzed Phe-Pip-Arg-pNA (S-2238, substrate for thrombin) more strongly than CBZ-Ile-Glu-Gly-Arg-pNA (S-2222, substrate for Factor Xa), CBZ-Phe-Val-Arg-pNA (B-7632) or CBZ-Pro-Phe-Arg-pNA (B-2133). Thrombin-like enzymes, beta-fibrinogenase and esterase hydrolyzed tosyl-L-arginine methyl ester and benzoyl-L-arginine ethyl ester. S-2238 is the most susceptible chromogenic substrate for most venom proteases. Thrombin-like enzymes degraded prothrombin molecule progressively down to prethrombin 2 while alpha- and beta-fibrinogenases degraded it only to prethrombin 1. Factor X activator of Vipera russelli venom and esterase of T. mucrosquamatus venom did not have any effect on prothrombin. Thus, the effects of venom proteases on prothrombin are not parallel to their amidolytic or esterolytic effects.