Plasmin-antiplasmin complex as a reservoir of fibrinolytic enzyme

Abstract

When streptokinase-activated, urokinase-activated, or spontaneously activated human plasmin is mixed with increasing amounts of human antiplasmin, caseinolytic effect decreases much more rapidly than fibrinolytic effect. At concentrations of antiplasmin at which caseinolytic effect completely disappears, considerable fibrinolytic activity persists. Authors suggest that fibrin can compete for plasmin with antiplasmin while other proteins may be less effective in this respect. This may explain the specificity of plasmin for fibrin in vivo, in the presence of the inhibitor. Antiplasmin may play an important physiological role in protecting normal plasma proteins while allowing lysis of fibrin clots by plasmin.