Direct Activation of Human Plasminogen by Streptokinase ∗

Abstract

Summary

Human plasminogen was treated with either DFP, TLCK, or SBTI under conditions which completely inhibited the plasmin contaminant in our preparation. Each treated plasminogen preparation could be completely activated with low molar ratios of streptokinase to plasminogen in 24 hr, in 25% glycerol. Activation of DFP-treated plasminogen with either streptokinase or a DFP-treated equimolar human plasmin-streptokinase complex could also be carried out in 10-² M DFP, in 25% glycerol; however, much longer periods of time were required to obtain nearly complete activation. Under these conditions for activation, the plasmin contaminant in our human plasminogen preparation is therefore not essential for streptokinase-activation of the proenzyme. These data indicate that streptokinase, alone or in the complex, acts directly on human plasminogen. A new electrophoretic method for differentiating human plasminogen from human plasmin is described.