INHIBITION OF THE ESTERASE, ACTIVATOR AND FIBRINOLYTIC-ACTIVITIES OF THE PLASMIN-STREPTOKINASE ACTIVATOR COMPLEX BY L-LYSINE

The effect of L-lysine on some reactions catalysed by plasmin and the plasmin-streptokinase activator complex has been studied. The constant s for competitive inhibition by L-lysine of the benzyloxycarbonyl-L-ly sine p-nitrophenyl ester hydrolysis by the activaior (K-i 116 mM), of the plasminogen activation by the activator( K-i 8 mM) and of fibrinol ysis by plasmin (K-i 3 mM) were determined. It was found that L-lysine at concentrations below 0,05 M, which do not affect the activator's e sterase activity, does inhibit fibrinolysis by plasmin and the activat or complex The effect of L-lysine on fibrinolysis under the action of the activator is complex: it inhibits both the activation of clot-entr apped plasminogen by the activator and lysis of fibrin by the plasmin formed. This inhibitory action of L-lysine is largely related to the f act that it lowers the sorption of the activator, plasminogen and plas min on fibrin, competing with fibrin for their lysine-binding sites as well as worsens the activator-plasminogen binding.