The action of echis carinatus venom on the blood coagulation system: Demonstration of an activator of factor X

E. carinatus venom activates both [human] coagulation factor II and coagulation factor X. The activation of both proenzymes by the venom is Ca2+-dependent& phospholipids are not necessary. The activation of factor II by the venom is a slow process and, in the absence of factor X, the clotting activity towards fibrinogen is generated only very slowly. Because E. carinatus venom clots plasma readily, under conditions in which the prothrombinase complex can be formed from the factor X activated by the venom, it is this complex rather than the venom itself that is responsible for the major part of the thrombin formation.