ACYL-COENZYME A CHOLESTEROL ACYLTRANSFERASE ACTIVITY IN HUMAN-LIVER

1. In the presence of CoA and ATP, human liver microsomes catalyse the incorporation of [14C]oleate or [14C]cholesterol into cholesteryl oleate, thus demonstrating the presence of acylcoenzyme A-cholesterol acyltransferase (cholesterol acyltransferase) in human liver. 2. The enzyme has properties similar to those of rat liver enzyme and with both the concentration of endogenous cholesterol in the microsomal fraction is adequate to support a constant initial rate of esterification. However, unlike the rat liver enzyme, the human cholesterol acyltransferase does not efficiently utilize added cholesterol as substrate. 3. The activity of cholesterol acyltransferase in human liver was 25% of that measured in rat liver under similar conditions of assay.