KINETICS OF FIBRINOLYSIS BY PLASMIN - INH IBITION BY THE PRODUCTS OF FIBRIN DEGRADATION

A kinetics of lysis of I-125-labeled fibrin coagulates by plasmin was studied. The strong competitive inhibition of fibrinolysis by the prod ucts of fibrin degradation was found. On the basis of the integral ana lysis of the complete kinetic curves of the fibrinolysis products accu mulation, the Michaelis constant K-m, the catalytic constant of the re action of fibrinolysis by plasmin k(cat), and the constant of inhibiti on by the reaction products K-i were determined to be 1.3 mu M, 1.36 m in(-1), and 0.12 mu M, respectively. The results obtained showed that the efficiency of plasmin inhibition by the reaction products exceeds that of plasmin interaction with the substrate. Thus, the process of f ibrinolysis is regulated by a negative feedback mechanism.