[Effect of dielectric permeability of culture media on the kinetics of the ATP hydrolysis reaction, catalyzed by Ca2+-transporting ATPase, solubilized from smooth muscle cell membrane].
Transport Ca2+,Mg(2+)-ATPase was solubilized from myometrial plasma membrane and purified by calmodulin-sepharose 4B affinity chromatography; the effect of dielectric permeability of incubation medium on kinetics of ATP hydrolysis by this enzyme was studied. Various concentrations of dimethylsulfoxide, ethanol, acetone, and dioxane (up to 10%) caused various dose-dependent inhibition of enzymatic ATP hydrolysis. The correlation between specific activity (A) of Ca2+,Mg(2+)-ATPase and dielectric permeability of the incubation medium (D) did not depend on the nature of organic solvents and was satisfactory approximated by similar lines in the Laidler-Scatchard coordinate system, i.e., ln(A) versus 1/D. Decrease in polarity of incubation medium (changes in D from 73.05 to 68.80) decreased the initial maximal rate of enzymatic reaction for ATP and Mg2+ and increased apparent Km for these compounds. Decrease in ionic strength of incubation medium from 100 to 25 mM KCl decreased the maximal initial rate of ATP hydrolysis for Ca2+ and increased the apparent Km for this cation. The data are discussed in conjunction with a model of transport Ca2+,Mg(2+)-ATPase active site structure.
Slinchenko
N N
NN
kinet@biochem.freenet.kiev.ua
Kosterin
S A
SA
Bogutskaia
E I
EI
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology; D003470:Culture Media; D004553:Electric Conductivity; D005260:Female; D006868:Hydrolysis; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology*; D009215:Myometrium / Q000201:enzymology
D003470:Culture Media; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases