of Action of Human Activated Protein C, a Thrombin-Dependent Anticoagulant Enzyme

Human protein C was purified. and the mechanism of action of activated protein C as an anticoagulant in plasma was studied. Protein C was purified from commercial factor IX concentrate by DEAE-Sephadex and dextran sulfate-Sepharose chromatography and preparative polyacrylamide gel electrophoresis. Purified protein C appeared homogenous at 62.000 mol wt on nonreduced SDS-polyacrylamide gels and. following reduction. protein C gave two polypeptide chains of 40.000 and 22.000 mol wt. Protein C was activated by immobilized trypsin or thrombin or by soluble thrombin. Activated protein C markedly prolonged the prothrombin time and the activated partial thromboplastin time of normal plasma. but had no effect on the thrombin time. Activated protein C exhibited amidolytic enzyme activity. DFP inhibited both the amidolytic and anticoagulant activities. Activated protein C was added to human plasma in the presence or