[Enzymatic fibrinolytic agents].

Urokinase (UK) and streptokinase (SK) transform plasminogen into plasmin by rupture of a ARG-VAL bond and the liberation of a peptide with a molecular weight of 6000 to 8000. Urokinase is a physiological activator with a direct action. By contrast, streptokinase is an enzyme of bacterial origin and two hypotheses may be advanced to explain its mechanism of action: the formation of a SK-plasminogen complex capable of activatiing new molecules of plasminogen or the formation of a SK-plasminogen complex within which plasminogen is transformed to plasmin.