Fibrinogenolytic properties of natrahagin (a proteinase from cobra venom) and its effect on human platelet aggregation

AIM: To study the fibrinogenolytic properties of natrahagin and its effect on platelet aggregation. METHOD: SDS-PAGE, fibrinogenolytic activity assay, platelet aggregation. RESULTS: Upon incubation of fibrinogen with natrahag in at the ratio of 50:1 (w/w), A(alpha)-chains of fibrinogen were almost co mpletely hydrolyzed in 5 min; however, at least 6 h was needed for the comp lete degradation of gamma-chains. Fibrinogenolytic activity of natrahagin w as 0.349 +/- 0.044 g.min(-1).g(-1) as determined by its ability to reduce t he clottable fibrinogen. On the other hand, natrahagin concentration-depend ently inhibited platelet aggregation induced by ristocetin in platelet-rich plasma and thrombin (80 U.L-1) in washed platelets with IC50 (95 % confide nce limit) of 56 (40-79) and 3.3 (1.4 -8.0) mg.L-1. No inhibitory effect wa s found on collagen- and ADP-induced platelet aggregation even when the dos e of natrahagin reached 200 mg.L-1 CONCLUSION: Natrahagin is an alpha, gamm a-fibrinogenase with an inhibitory effect on platelet membrane glycoprotein Ib (GPIb)-dependent platelet aggregation.