Shkrabak O. The influence of calixarenes on ATP-hydrolyzing systems of myometrium plasma membrane and on nonenzymatic hydrolysis of ATP

Object: plasma membrane fraction of pig myometrium, reactions of enzymatic (Na+,K+- and Mg2+-dependent) and nonenzymatic ATP hydrolysis. Aim: to study the calixarene effects on Na+,K+-АТРase and "basal" Mg2+-ATPase activities in the plasmatic membrane of the uterus smooth muscle cells and on nonenzymatic hydrolysis of ATP. It was shown that high effective selective inhibition of Na+,K+-АТРase by calyx[4]arene C-107 was caused by the cooperative action of two aminophosphonic substituents spatially oriented at the distal position on the upper rim of the calixarene bowl. This calixarene and calixarene C-97 enhance the inhibition of Na+,K+-АТРase by ouabain. The investigation of membrane effects of calixarenes showed that calixarene C-107 caused the agglutination of membrane vesicles. The influence of calixarene C-99 on the fluorescence response of the voltage-sensitive fluorescent probe DiOC6(3) depends on membrane polarization in the K+/valinomycin system. It was discovered that calixarenes С-107, С-91 and С-160 were able to stimulate nonenzymatic hydrolysis of ATP. The kinetic and catalytic properties of this reaction have been studied with calixarene C-107.