On the Occurrence of a Plasminogen

P LASMINOGEN is a proenzyme of blood plasma, which under the influence of different activators, or even spontaneously, can be converted into th& enzyme called plasmin. Spontaneous activation: streptokinase 1 plasminogen staphylokinase _______________ serokinase fibrinokinase plasmin Astrup and M#{252}llertz’ and M#{252}llertz and LassenTM have proposed another schema for the fibrinolytic system. Their starting point was the observation that streptokinase (SK) does not activate bovine plasma at all, and yields only small amounts of plasmin when incubated with human globulins. When a mixture of bovine plasma and human globulins is incubated with SK, however, large amounts of plasmin are formed. These authors suggest the existence of a proactivator and an activator of plasmin in human plasma. SK acts only on the proactivator, transforming it into the activator. The activator reacts with plasminogen and transforms it into plasmin. SK is not able to activate bovine plasma because bovine plasma is lacking in adequate amounts of proactivator. The corrected schema of fibrinolysis would then be as follows: SK proactivator activator