Substrate Specificity of Lecithin:Cholesterol Acyltransferase Esterification of Desmosterol, β-Sitosterol, and Cholecalciferol in Human Plasma

Abstract

Desmosterol and β-sitosterol were esterified when incubated with normal human plasma. The initial rate of desmosterol esterification was 1.7 times faster, and that of β-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 β-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.

Key Words:

• β-sitosterol
• cholecalciferol
• cholesterol
• desmosterol
• lecithin
• cholesterol acyltransferase
• lipoproteins
• sterols