title: [Protein C, protein S].
abstract: Protein C is a potent inhibitor of blood coagulation, and, in addition, appears to be a profibrinolytic agent. In a first step, protein C must be converted to a serine protease. This activation is catalyzed by a complex formed between thrombin and thrombomodulin, an endothelial cell surface protein. Activated protein C exhibits its anticoagulant activity through the proteolytic inactivation of two blood coagulation cofactors, factors Va and VIIIa. This reaction requires phospholipids, originating from platelets or endothelial cells, and a cofactor protein, protein S. Protein S enhances the binding of activated protein C to phospholipids. In addition, activated protein C stimulates fibrinolysis, through the inactivation of the tissue plasminogen activator (tPA) inhibitor. An isolated constitutional, quantitative or qualitative, protein C or protein S deficiency increases the risk of thrombosis, the clinical features are different in the rare cases of homozygous protein C deficiency (neonatal purpura fulminans) or in the heterozygous patients (recurrent venous thrombosis in young adults). Acquired deficiency in protein C and S had been observed in liver disease, during vitamin K antagonists or L-Asparaginase treatment, and in disseminated intravascular coagulation.
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D055598:Chemical Phenomena; D002621:Chemistry; D004727:Endothelium / Q000378:metabolism; D006023:Glycoproteins / Q000172:deficiency; D006801:Humans; D011486:Protein C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D020151:Protein C Deficiency; D017293:Protein S; D011956:Receptors, Cell Surface / Q000378:metabolism; D018179:Receptors, Thrombin; D013917:Thrombin / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D011486:Protein C; D017293:Protein S; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D013917:Thrombin
vernacular_title: Protéine C, protéine S.