T. O. Veklich¹, O. A. Shkrabak¹, R. V. Rodik²,
V. I. Kalchenko², S. O. Kosterin¹

¹Palladin Institute of Biochemistry, National Academy
of Sciences of Ukraine, Kyiv;
²Institute of Organic Chemistry, National Academy
of Sciences of Ukraine, Kyiv;
e-mail: kinet@biochem.kiev.ua; vik@bpci.kiev.ua

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 was investigated. It has been shown that the calixarene C-107 inhibiting Na⁺,K⁺-ATPase does not change the kinetic parameters (K_m, n_H) of reaction velocity dependence on substrate concentration. The constant K_a of enzyme activation by MgCl₂ has complex dependence on calixarene C-107 concentration: it increases twice with growth of calixarene concentration up to 50 nM and decreases to the control level with further growth of calixarene concentration. The Hill cooperativity coefficient n_H of activation by MgCl₂ does not vary in the presence of calixarene C-107. Both ATP and MgCl₂ have no influence on Na⁺,K⁺-АТРase constant of inhibition by calixarene C-107, but an increase of concentration of the mentioned physiological compounds causes the growth of cooperativity coefficient nH of enzymatic reaction inhibition by calixaren C-107.