EFFECT OF EOSIN Y ON MYOMETRIUM ACTOMYOSIN ATPase ACTIVITY
R. D. Labyntseva, S. O. Kosterin
The effect of the reversible inhibitor of membrane-bound Ca2+-transporting system in smooth muscle – eosin Y – on apparent kinetic parameters that characterize the sensitivity to Mg2+ of myometrium actomyosine ATPase reaction was investigated. It is shown that eosin Y decreases an affinity of actomyosin for Mg2+ and does not influence the number of turns of the smooth muscle actomyosin ATPase activity that was defined by Mg2+. This suggests possible competition of eosin Y with Mg2+ for the active center of actomyosin ATPase. However, the negatively charged inhibitor cannot be adsorbed on Mg2+-binding site of the active center because of essential differences in size, form and charge between eosin Y and Mg2+. Most likely, eosin Y acts on uterus smooth muscle actomyosin as an allosteric inhibitor. Consequently, the mechanism of eosin Y action on ATPase activity of myometrium contractile proteins is different from the mechanism of its influence on ATP-hydrolase enzyme systems of plasmatic membranes.
Key words: ATPase activity, Mg2+, eosin Y, actomyosin, smooth muscle, uterus.
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