Influence of SK-potentiator and fibrinogen degradation products on the activation of human plasminogen by streptokinase

When fibrinogen was degraded by plasmin, very early degradation products (FgDP-5′) enhanced the activity of SK-activator (SK-plasminogen or SK-plasmin) to the largest extent, and further degradation, such as extentsive degradation of β-chain (FgDP-20′), resulted in less enhancement of SK-activator activity than fibrinogen itself which also enhanced it. Fibrin enhanced the activation rate of plasminogen by SK to the largest extent, more than SK-potentiator. The action of thrombin on SK-potentiator was as effective as fibrin in the enhancement, thus removal of fibrinopeptides from fibrinogen or SK-potentiator is important in the activator activity of the trimolecular complex of SK-plasminogen-potentiator. SDS-PAGE indicated that native plasminogen was converted to plasmin faster in the presence of SK and SK-potentiator than SK alone.