Journal archive > 2009 > N 1 January-February
R. D. Labyntseva, O. M. Bobrovska, A. A. Bevza, S. O. Kosterin
Influence of dielectric permeability аnd incubation medium temperature on sensitivity of ATPase of contractile protein complex to eosin Y was studied on preparations of uterine smooth muscle actomyosin. It was shown, that a decrease of dielectric permeability from 74.1 tо 68.8 is accompanied by inhibition of activity of actomyosin ATPase by 30%. Administration of eosin Y to the incubation medium intensifies the inhibition of activity of actomyosin ATPase, that correlates with a decrease of dielectric permeability and increase of eosin Y concentration. Catalytic titration of actomyosin ATPase by eosin Y (from 10-7 tо 10-5?М) on the background of a change of dielectric permeability (from 741 tо 68.8) shows, that curve of dependence of ATPase activity on the inhibitor concentration is characterized by a lower value of enzymatic activity and its quicker decay at D 68.8 than at D 74.1. Under a decrease of dielectric permeability from 74.1 tо 68.8 the observed decrease of the value of inhibition coefficient from 0.74 ±?0.07 tо 0.10 ± 0.01 мкM, that can evidence for the essential role of electrostatic interactions in the binding of eosin Y with smooth muscle actomyosin. Studies of energy aspects of the mechanism of an eosin Y action on ATP-hydrolase activity of smooth muscle contractive proteins (determination of temperature dependence and activation energy Eo) show that the inhibitory effect of eosin?Y on myometrium actomyosin ATPase activity is connected with an increase of the reaction energy barrier. That is, the effect of eosin Y on actomyosin ATPase activity is shown not only on catalytic but also on thermodynamic levels.
Key words: АТРаse, actomyosin, eosin Y, dielectric permeability, temperature dependence, activation energy Eo, smooth muscle.
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