Biopolymers and cell. 1990. Volume 6. № 3. 59 - 65

I. V. Pekhnik, M. Yu. Selishcheva, A. A. Sereyskaya

THE EFFECT OF IONIC STRENGTH ON ENZYMATIC ACTIVITY OF THROMBIN

Summary

    The dependence of human a-thrombin and its non-clotting y-form activity have been stu¬died for their dependence on ionic strength of the medium relative to the action on fib-rinogen and low-molecular tripeptide substrate. The previously found Rotoli effect of stimulation of fibrinogen clotting by thrombin with ionic strength much lower as against its physiological level (up to I 0.05) is confirmed. Acceleration of both fibrinogen pro-teolysis by thrombin and the non-enzymic stage of the process, namely, polymerization of fibrin monomer was shown to underlie this phenomenon. During the low-molecular substrate hydrolysis by both forms of thrombin and trypsin no low ionic strength stimu¬lation was observed. The data obtained permit concluding that due to the ionic strength decrease the conditions favourable for thrombin specific interaction (outside its active centre) with fibrinogen by means of long distrance electrostatic coupling between them are created.