Properties of a solubilised and reconstituted preparation of acyl-CoA:cholesterol acyltransferase from rat liver.

Rat liver acyl-CoA:cholesterol acyltransferase activity was released from the microsomal fraction by treatment with Triton X-100. After fractionation with polyethylene glycol 6000, the solubilised preparation was reconstituted in liposomes of different lipid composition by an octyl glucoside dilution method. The activity of the reconstituted system was dependent on the amount of cholesterol used in the liposomes and could also be stimulated by transfer of cholesterol into the reconstituted system from other membranes. The results are consistent with the hypothesis that substrate supply and the fluidity of the membrane contribute in the regulation of the rate of cholesterol ester formation.