title: Protein S and the regulation of activated protein C.
abstract: The studies that have been carried out to date suggest that protein S can function as a cofactor protein in the activated protein C catalyzed inactivation of Factor Va. This conclusion is supported by the observation that protein S and activated protein C can form a lipid bound complex that can inactivate Factor Va more rapidly than does soluble activated protein C. Protein S has a number of properties in common with other cofactor proteins. It has been isolated as a distinct entity from plasma, it has no known intrinsic activities, and its effect is maximal when it is bound to a lipid surface. Protein S appears to be important in the regulation of the plasma anticoagulant activity of activated protein C as well. This is supported by the lack of anticoagulant activity of activated protein C in protein S-depleted plasma and by the observation that protein S is important in the species specificity of the anticoagulant activity of the enzyme. Future work in this area is needed to ascertain if there are any clinical manifestations of protein S deficiencies that correlate with the cofactor activity that has been established.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001777:Blood Coagulation; D001779:Blood Coagulation Factors; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D010450:Endopeptidases; D004789:Enzyme Activation; D005165:Factor V / Q000037:antagonists & inhibitors; D015943:Factor Va; D005453:Fluorescence; D006023:Glycoproteins / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D008081:Liposomes; D010743:Phospholipids / Q000378:metabolism; D011486:Protein C; D017293:Protein S; D012697:Serine Endopeptidases; D012996:Solutions; D013045:Species Specificity; D013917:Thrombin / Q000494:pharmacology; D014812:Vitamin K / Q000494:pharmacology
chemical_list: D001779:Blood Coagulation Factors; D006023:Glycoproteins; D008081:Liposomes; D010743:Phospholipids; D011486:Protein C; D017293:Protein S; D012996:Solutions; D014812:Vitamin K; D015943:Factor Va; D005165:Factor V; D010450:Endopeptidases; D012697:Serine Endopeptidases; D013917:Thrombin; D002118:Calcium