Abstract: Reciprocal activation of prourokinase and plasminogen is an important mechanism in the initiation and propagation of local fibrinolytic activity. We have found that glucosyldiacylglycerol enhanced the reciprocal activation of both zymogens to active two-chain forms. The reciprocal activation system consists of (i) plasminogen activation by prourokinase to form plasmin, (ii) prourokinase activation by the resulting plasmin to form two-chain urokinase and (iii) plasminogen activation by the resulting urokinase-type prasminogen activator. Whereas glucosyldiacylglycerol minimally affected steps (ii) and (iii) in isolated systems, glucosyldiacylglycerol markedly enhanced plasminogen activation by prourokinase to form plasmin in the absence of the conversion of prourokinase to two-chain urokinase. Glucosyldiacylglycerol significantly increased intrinsic fluorescence of prourokinase, but not of two-chain urokinase and plasminogen. The large change in intrinsic fluorescence suggeststhat glucosyldiacylglycerol selectively affects prourokinase to alter its conformation, and this mechanism may account for enhancement of its intrinsic plasminogen activator activity. Glucosyldiacylglycerol significantly enhanced the fibrinolytic activationo ff ibrinc lots inv itro.

Key words: glucosyldiacylglycerol, prourokinase, plasminogen, fibrinolysis