Thrombolytic properties of an inactive proenzyme form of human urokinase secreted from human kidney cells.

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Abstract
The relative fibrin-binding, fibrinolytic and fibrinogenolytic properties of single-chain pro-urokinase, an inactive proenzyme form of human urokinase purified from cultured human kidney cells, and urokinase were compared. The affinity of single-chain pro-urokinase for fibrin was much higher than that of urokinase. In vitro thrombolytic studies showed that single-chain pro-urokinase is .apprx. 3 times more potent in fibrinolysis than urokinase and that it does not degrade fibrinogen in the plasma at a concentration at which complete plasma clot lysis takes place. Urokinase extensively degrades the fibrinogen in the plasma. These specific, potent thrombolytic properties of single-chain pro-urokinase seem to be due to its high affinity for fibrin and to its conversion from the inactive single-chain form to the active 2-chain form on the thrombus by the catalytic amount of plasmin generated during coagulation. This single chain pro-urokinase obtained from human kidney cells by tissue culture should prove more advantageous than urokinase in thrombolytic therapy.