[Identification and characterization of "basal" Ca2+-independent Mg2+-dependent ATP-hydrolase enzymatic activity in smooth muscle cell plasma membrane fractions].
It is shown, that for correct definition of "basal" Ca(2+)-independent Mg(2+)-dependent ATPase ac-activity (10-13 mmol Pi/hour on 1 mg of protein) in a fraction of uterus smooth muscle cell plasma membranes is necessary to use in medium without calcium of an incubation not only EGTA and digitonin--of the factor of infringement in activity by this subcellular structure, but inhibitors of others Mg(2+)-dependent ATP-hydrolyse enzymatic systems localized as in plasma membrane (Na+, K(+)-ATPase) and in others subcellular frames, first of all, in mitochondria (Mg(2+)-ATPase) and endoplasmic reticulum (transport Ca2+, Mg(2+)-ATPase). In the case of a sacolemal fraction of a smooth muscle the contribution of others Mg(2+)-dependent ATP-hydrolyse systems in a common enzymatic hydrolysis ATP, which unconnected to functioning "basal" Ca(2+)-independent Mg(2+)-dependent ATPase, is very appreciable and achieves 35%. The researches, carried out in the frameworks of definition of initial velocity of enzymatic reaction, have enabled to define its some properties--cationic and anionic specificity, and also sensitivity to action of some inhibitors. It has appeared, that the "basal" Ca(2+)-independent Mg(2+)-dependent ATP-hydrolyse reaction is nonspecific rather both in relation to cations of divalent metals Me2+, and cations of monovalent metals and anions, which were utilized for support of ionic strength. The cations La--antagonist of cations Ca--practically did not influence enzymatic activity. The non-specific inhibitors transport of ATPases--p-chloromercuribenzoate, o-vanadate and eosine Y with a various degree of efficiency inhibited "basal" Ca(2+)-independent Mg(2+)-dependent ATP-hydrolyse reaction. On the basis of the analysis of the own and literary data the conclusion is made that "basal" Ca(2+)-independent Mg(2+)-dependent ATPase of a smooth muscle cell plasma membrane is considerably less sensitive to action of nonspecific inhibitors of the Ca(2+)-transporting systems, than these systems.
Palladin Institute of Biochemistry, NAS of Ukraine, Kyiv.
H V
HV
Danylovych
S O
SO
Kosterin
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006867:Hydrolases / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D013552:Swine
D004791:Enzyme Inhibitors; D000255:Adenosine Triphosphate; D006867:Hydrolases; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium