Formation of Autoprothrombin in Solutions Containing Purified Prothrombin and Purified Platelet Factor 3

Abstract

By means of Ca ions and a purified preparation of platelet factor 3, purified prothrombin was converted to an "inactive" derivative. All attempts to obtain thrombin from this derivative failed, except by autocatalysis in a 25% solution of sodium citrate. When the prothrombin derivative forms, a powerful accelerator of prothrombin activation arises and this is referred to as the formation of autoprothrombin. After the derivative is transformed to thrombin by autocatalysis in sodium citrate solution no accelerator properties remain. Autoprothrombin accelerates the interaction of prothrombin, thromboplastin, and serum Ac-globulin; and the interaction of prothrombin, thromboplastin, and platelet accelerator (platelet factor I). It apparently does not accelerate the interaction of prothrombin, platelet factor 3, platelet co-factor I, and serum Ac-globulin. Likewise it does not accelerate the interaction of prothrombin, platelet factor 3, platelet cofactor II, and serum Ac-globulin. It is believed that autoprothrombin is derived from prothrombin and that these observations are related to concepts expressed by such terms as SPCA precursor, SPCA, proconvertin, convertin, factor VII, stable factor, co-thromboplastin, hyperactive prothrombin, and prothrombinogen.