The PROC gene encodes protein C (EC 3.4.21.69), a vitamin K-dependent plasma glycoprotein that is a key component of the anticoagulant system. Protein C is cleaved to its activated form, 'activated protein C' (APC) on endothelial cells by the thrombin-thrombomodulin complex (MIM 176930; MIM 188040) and then acts as a serine protease to degrade the activated forms of coagulation factors V (F5; MIM 612309) and VIII (F8; see MIM 306700). Protein S (PROS1; MIM 176880), also a vitamin K-dependent plasma protein, functions as a cofactor to activated protein C.[supplied by OMIM]