Substrate specificity of lecithin:cholesterol acyltransferase. Esterification of desmosterol, b-sitosterol, and cholecalciferol in human plasma.

Desmosterol and beta-sitosterol were esterified when incubated with normal human plasma. The initial rate of demosterol esterification was 1.7 times faster, and that of beta-sitosterol 0.4 times slower, than the esterification rate of cholesterol. These ratios were found to be almost the same when plasma from different normal individuals was tested. Plasma from a patient with familial lecithin:cholesterol acyltransferase deficiency did not esterify any of the sterols. The esterification of desmosterol and beta-sitosterol was considerably slower in normal plasma in which in vitro cholesterol esterification previously had taken place. The different esterification rates could not be explained by a different affinity of the plasma lipoproteins for the sterols tested. Cholecalciferol added to normal plasma did not become esterified.