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THE EFFECT OF CALIXARENE C-107 ON KINETIC
CHARACTERISTICS OF Nа + ,К +
-АТРase OF MYOMETRIUM
PLASMA MEMBRANE
Shkrabak O.A. 1 , Veklich T.O. 1 2
, Rodik R.V.
1 Palladin Institute of Biochemistry, NASU, Kyiv; e-mail: veklich@biochem.kiev.ua
2 Institute of Organic Chemistry, NASU, Kyiv; e-mail: manli@ioch.kiev.ua
We investigated the inhibitory action of calixarene C-107 (5,17-diamino(2-
pyridyl)methylphosphono-11,23-di-tret-butyl-26,28-dihydroxy-25,27-
dipropoxycalix[4]arene) on Na + ,K + -ATPase activity kinetic properties of myometrium
perforated plasma membrane. It was shown that this calixarene, inhibiting Na + ,K + -
ATPase, did not change the kinetic parameters (Km, nH) of reaction velocity dependence
on substrate concentration. The constant КMg of enzyme activation by MgCl2 had
complex dependence on calixarene C-107 concentration: increased twice from 173 ± 4
µM to 375 ± 43 µM with growth of calixarene concentration up to 50 nM and decreased
to control level with further growth of calixarene concentration to 100 nM. The Hill
cooperativity coefficient nH of activation by MgCl2 did not vary in the presence of
mentioned calixarene. Both ATP and MgCl2 had no influence on Na + ,K + -АТРase
constant of inhibition by calixarene C-107, but the concentration increase of mentioned
physiological compounds caused the growth of cooperativity coefficient nH of
enzymatic reaction inhibition by calixarene C-107. It was also shown that this
calixarene increased the affinity of the enzyme to the sodium pump conventional
inhibitor - ouabain: the magnitudes of the apparent constant of inhibition I0.5 changed
from 26.9 ± 1.3 µM to 10.9 ± 0.6 µM. However, the ouabain itself did not influence on
the affinity of the Nа + ,K +
-АТРase to сalixarene С-107.
Therefore, we can conclude that inhibitory action of calixarene C-107 on Na
ATPase has uncompetitive character and, perhaps, interaction of calixarene C-107 with
enzyme leads to decrease of enzyme turnover number.
+ ,K +
We are thankful to corresponding members of NASU V.I. Kalchenko and S.O.
Kosterin for helpful discussion and scientific cooperation.
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