title: Antithrombin III, protein C, and protein S. Naturally occurring anticoagulant proteins.
abstract: Protein C, protein S, and antithrombin III are naturally occurring anticoagulant proteins. Activated protein C and protein S act by inhibiting the action of the cofactors factor Va and factor VIIIa. Antithrombin III inhibits the serine proteases (factors II, IX, X, XI, and XII); its anticoagulant action is dramatically enhanced by heparin. Deficiencies of these proteins are associated with thromboembolic disease. Antigen and activity assays practical for the clinical laboratory are available for protein C and antithrombin III. Protein S antigen assays are also available. Diagnosis of an anticoagulant protein deficiency has serious implications for a patient and his kindred, and should therefore only be made on the basis of repeated abnormal determinations of a single protein in an individual patient, or documentation of the same protein deficiency in other family members.
mesh_terms: D000990:Antithrombin III / Q000032:analysis / Q000502:physiology*; D020152:Antithrombin III Deficiency; D001777:Blood Coagulation; D001778:Blood Coagulation Disorders / Q000175:diagnosis / Q000235:genetics; D006023:Glycoproteins / Q000032:analysis / Q000172:deficiency / Q000502:physiology*; D006801:Humans; D008722:Methods; D011486:Protein C / Q000032:analysis / Q000502:physiology*; D020151:Protein C Deficiency; D017293:Protein S
chemical_list: D006023:Glycoproteins; D011486:Protein C; D017293:Protein S; D000990:Antithrombin III