Thrombin formation; effects of lysin (fibrinolysin, plasmin) on prothrombin, Ac-globulin and tissue thromboplastin.

In the course of a study of the blood coagulation reaction involving the use of partially purified reagents it was thought of some interest to determine effects of fibrinolytic enzyme on these isolated materials. It is well known that serum lysin (fibrinolysin, plasmin) will lyse or destroy both fibrinogen and fibrin. It may be thrombinolytic (1). Seegers and Loomis (2) have stated that it destroys prothrombin. In the present study we have compared the effects of lysin on prothrombin, Ac-globulin and tissue thromboplastin. In choosing a lysin for these studies it was necessary to find a preparation active fibrinolytically but free from thrombin and antithrombin. A preparation of Loomis' (3) fibrinolysin was satisfactory in these respects. Human Fraction III-3 (4) and our dog serum lysin (5) both contained appreciable quantities of thrombin.