[Inhibition of esterase by L-lysine, the activator and fibrinolytic activity of the plasmin-streptokinase activator complex].

The effect of L-lysine on some reactions catalysed by plasmin and the plasmin-streptokinase activator complex has been studied. The constants for competitive inhibition by L-lysine of the benzyloxycarbonyl-L-lysine p-nitrophenyl ester hydrolysis by the activator (Ki 116 mM), of the plasminogen activation by the activator (Ki 8 mM) and of fibrinolysis by plasmin (Ki 3 mM) were determined. It was found that L-lysine at concentrations below 0.05 M, which do not affect the activator's esterase activity, does inhibit fibrinolysis by plasmin and the activator complex. The effect of L-lysine on fibrinolysis under the action of the activator is complex: it inhibits both the activation of clot-entrapped plasminogen by the activator and lysis of fibrin by the plasmin formed. This inhibitory action of L-lysine is largely related to the fact that it lowers the sorption of the activator, plasminogen and plasmin on fibrin, competing with fibrin for their lysine-binding sites as well as worsens the activator-plasminogen binding.