Effect of cholesterol sulfate and sodium dodecyl sulfate on lecithin-cholesterol acyltransferase in human plasma

The effects of cholesterol sulfate and sodium dodecyl sulfate (SDS) on the esterification of cholesterol in sonicated dispersions of lecithin-cholesterol mixtures by lecithin-cholesterol acyltransferase [EC 2.3.1.43] (LCAT) in human plasma were studied in vitro. The acyltransferase activity was inhibited at concentrations of cholesterol sulfate higher than 1 X 10(-4) M. This inhibition was not eliminated by the addition of bovine serum albumin or CaC12. On the contrary, the acyltransferase activity was stimulated at concentrations of SDS ranging from 1 X 10(-5) M to 1 X 10(-3) M, and maximum stimulation was obtained at 5 X 10(-4) M. The maximum stimulation disappeared on the addition of bovine serum albumin (30 mg per ml of incubation medium), 1 X 10(-3) M CaC12 or 1 X 10(-4) M cholesterol sulfate. On the other hand, the extent of inhibition of the acyltransferase by cholesterol sulfate was not affected by the amount of lecithin in the dispersion added as a substrate, but the maximum stimulation (5 X 10(-4) M SDS) of the acyltransferase was interfered with when a large amount of lecithin was present in the dispersion. In addition, the amount of SDS required for maximum cholesterol esterification was not affected by the amount of lecithin present in the dispersion. These results suggest that the action of cholesterol sulfate on the acyltransferase is different from that of SDS.