The effect of biologically active compounds on the enzymatic activity of sarcoplasmic reticulum (Ca2+,Mg2+)-dependent ATPase transformed by synthetic phospholipids

Aminasine, BeSO4 and Pt-5-sulfomercaptoquinolinate action on Ca-ATPase of SR showed a considerably less inhibiting effect as compared with that produced on the native membranes. The inhibiting action of the chemical compounds on those of native SR membranes is followed by the increase of mobility of hydrophobic segments of the membrane. The kinetic study of ATPase reaction at various temperatures showed on low-temperature transformation after the action by chemical compounds. Both structural transformations retain in the modified SR membrane independent of the chemical treatment. The activation energies considerably differ from those of native an modified membranes without chemical treatment (particularly in the region of 10-20 degrees). The data obtained allow to suggest that the inhibiting action of chemical compounds is followed by the changes in microviscosity (in the region of protein-lipid interaction of SR membrane, in particular), which by conformation transformations affect the configuration of the enzyme active center, alternating its geometry and catalytic activity.