The effect of changes of the content of membrane cholesterol and the effect of benzyl alcohol on the activity of the intrinsic Mg2+-ATPase from the erythrocyte plasma membrane of the flounder (Platichthys flesus L.).
Extraction of membrane cholesterol and incorporation of cholesteryl hemisuccinate into the membrane affect the activity of the membrane-bound Mg2+-ATPase. Increasing the ratio of cholesterol to phospholipid from 0.30 mg/mg in the control membranes to 0.45-0.90 in the enriched membranes results in a slight increase of the activity of about 20%. Diminishing the ratio of cholesterol to phospholipid to about one tenth of the ratio of the control membrane results in a decrease of the activity to about 30% of the untreated control. Benzyl alcohol inactivates the membrane-bound enzyme. Digitonin-solubilized Mg2+-ATPase is also inactivated by benzyl alcohol. For concentrations below 20 mM the dependence of the solubilized and the membrane-bound enzymes are virtually identical, and linearly dependent on alcohol concentration. This linear relationship continues up to 70 mM for the solubilized enzyme, while inhibition of the membrane-bound form shows a slightly steeper dependence on inhibitor concentration. It is suggested that the activity of the native Mg2+-ATPase depends on the organization of the lipid phase of the membrane and that addition of benzyl alcohol or depletion of cholesterol results in a disorganization of the lipid phase which in turn results in diminished activity.
D000818:Animals; D019905:Benzyl Alcohol; D001592:Benzyl Alcohols / Q000494:pharmacology*; D001593:Benzyl Compounds / Q000494:pharmacology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000097:blood*; D002784:Cholesterol / Q000097:blood*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D005399:Fishes; D007700:Kinetics; D008563:Membrane Lipids / Q000097:blood*
D001592:Benzyl Alcohols; D001593:Benzyl Compounds; D008563:Membrane Lipids; D002784:Cholesterol; D017301:Ca(2+) Mg(2+)-ATPase; D019905:Benzyl Alcohol