ABSTRACT
This chapter deals with the discovery of protein C activators from snake venoms, their chemical properties, mode of action, and application. However, before the authors turn their attention to these highly interesting substances, they start with some general comments on the physiological role of protein C. Thrombin without any cofactor causes a slow activation of protein C that is about 20,000-fold accelerated by thrombomodulin and that is inhibited by calcium ions. Biochemical laboratory findings indicating the anticoagulant and profibrinolytic potential of protein C led to the hypothesis that a deficiency of this protein might be accompanied by thromboembolic disease. Crude A. contortrix venom is a complex protein mixture containing several interacting procoagulant, anticoagulant, and fibrin(ogen)olytic components. The protein C activator from A. contortrix venom directly and independently from any cofactor converts the zymogen protein C in human plasma into a proteinase with the enzymatic and anticoagulant properties of protein Ca activated by thrombin.
