Autocatalysis in prothrombin activation

¹ Department of Physiology and Pharmacology, Wayne State University, College of Medicine, Detroit, Michigan

Two enzymes, thrombin and autoprothrombin C, are derived from purified prothrombin by autocatalytic activation in 25% sodium citrate solution. The thrombin but not the autoprothrombin C activity is destroyed by diisopropylfluorophosphate. Autoprothrombin C is a procoagulant, which catalyzes the conversion of prothrombin to thrombin in a prothrombin-activating mixture consisting of calcium ions, Ac-globulin, and crude cephalin. Depending upon the amount of p-toluenesulphonyl-l-arginine methyl ester added to the prothrombin-activation mixture the thrombin generation may be retarded or inhibited completely. The view is expressed that all prothrombin activations are fundamentally autocatalytic. The end products of prothrombin activation involved are autoprothrombin C and thrombin, while the intermediate products of prothrombin activation are the autoprothrombins.