Protein C

Protein C is an endogenously occurring plasma protein that plays a key role within the coagulation cascade. Protein C is a zymogen, or enzyme precursor, of a vitamin K-dependent anticoagulant glycoprotein (serine protease) that is synthesized in the liver. It is converted by the thrombin/thrombomodulin-complex on the endothelial cell surface to Activated Protein C (APC). Once in its activated form, APC functions as a serine protease with potent anticoagulant effects, especially in the presence of its cofactor protein S. APC exerts its effect by inactivating essential components of the coagulation cascade (specifically factors V and VIII), which leads to a decrease in thrombin formation, and therefore a reduction in clot formation. The Protein C pathway provides a natural mechanism for control of the coagulation system and prevention of excessive procoagulant responses to activating stimuli. A lack of protein C in the body would lead to unchecked coagulation activation, resulting in thrombin generation and intravascular clot formation. Protein C is available in concentrated form as the product Ceprotin, which is indicated for use in pediatric and adult patients with severe congenital protein C deficiency for the prevention and treatment of venous thrombosis and purpura fulminans.