[pH-dependence of inhibitory action of eosin Y on ATPase activity of smooth muscle actomyosin complex of the uterus].

Research of pH-dependence of inhibitory action of eosin Y (2',4',5',7'-tetrabromofluorescin) on ATPase of contractile proteins of smooth muscles of the uterus has shown that the increase of concentration of this inhibitor (from 0.1 to 10 microM) influenced the profile of pH-dependence of ATPase activity of actomyosin: in the presence of 0.1 microM eosin Y the change of optimal value of pH has been observed in more sour side in relation to the control; at the increase of concentration of eosin Y (from 0.5 to 10 microM) the strongly pronounced optimum of pH is absents in general. The ability of eosin Y to inhibit the ATPase activity of contractile complex is dependent on pH of incubation environment. The change of pH from 6.0 to 7.2 results in a 9-fold decrease of magnitude of apparent constant of inhibition Ki (from 6.5 +/- 0.8 microM to 0.74 +/- 0.07 microM). The obtained results indicate that the diminishing of concentration of H+ in an incubation environment favors the increase of affinity ATPase of actomyosin for eosin Y and prove the important role of ionization processes in the system "enzyme-substrate-inhibitor" for realization of inhibitory action of eosin Y.