Alpha and beta-fibrinogenases from Trimeresurus gramineus snake venom

By means of DEAE-Sephadex A-50 Column chromatography, Trimeresurus gramineus venom was separated into twelve fractions. The fibrinogenolytic activities were distributed in Fractions 1 and 10. These enzymes were further purified by gel filtration and were homogeneous as judged by cellulose acetate membrane, sodium dodecyl sulfate polyacrylamide gel electrophoresis and ultracentrifugal analysis. Both of them were single peptide chains. The sedimentation constants of alpha- (Fraction 1) and beta-fibrinogenases (Fraction 10) were 2.20 and 3.60, respectively. The molecular weights of alpha- and beta-fibrinogenases were 23 500 and 25 000 respectively. The contents of proline and glycine were higher in beta-fibrinogenase than in alpha-fibrinogenase. The isoelectric points of alpha-fibrinogenase and beta-fibrinogenase were pH greater than 10 and 4.5, respectively. The optimal pH of alpha-fibrinogenase was approx. 7.4 and that of beta-fibrinogenase was approx. 9.0. The activity of alpha-fibrinogenase was completely destroyed after 30 min at 60 degrees C, pH 5.4, 7.4 and 9.0, while that of beta-fibrinogenase was much less affected by the same treatment. The specific fibrinogenolytic activity alpha-fibrinogenase was 31 mg fibrinogen/min per mg protein, while that of beta-fibrinogenase was 9 mg fibrinogen/min per mg protein. alpha-Fibrinogenase cleaved specifically the alpha(A) chain of monomeric fibrinogen without cleaving the beta(B) chain and gamma-chain. beta-fibrinogenase preferentially cleaved the beta(B) chain, and the alpha(A) chain was also partially cleaved by beta-fibrinogenase, if the incubation time was prolonged. Both enzymes showed proteolytic activities toward fibrinogen, fibrin and casein, but were devoid of phospholipase A, alkaline phosphomonoesterase and phosphodiesterase activities found in the crude venom. The tosyl-L-arginine methylester esterase activity of beta-fibrinogenase was about 14 times that of crude venom, while alpha-fibrinogenase was completely devoid of this activity. The fibrinogenolytic activity of alpha-fibrinogenase was markedly inhibited by EDTA and cysteine, while that of beta-fibrinogenase was inhibited markedly by phenylmethanesulfonylfluoride. alpha- and beta-fibrinogenases exert their fibrinogenolytic activity by a direct action on fibrinogen or fibrin without activation of plasminogen.