Studies on enzymatic and molecular properties of lecithin: Cholesterol acyltransferase

I. Cholesterol esterification in human serum was measured in healthy male and female subjects using a modified version (2) of the Stokke & Norum assay technique (1). Strong positive correlation was observed between the rate of cholesterol esterification and serum free cholesterol esterification (^rp = 93, p < 0.001 for males: ^rp = 81, p < 0.001 for females), suggesting that the fractional rate of esterification is a more useful parameter for comparative studies than the rate of esterification. II. Purification and characterization of LCAT. Highly purified LCAT preparations were obtained by using the combined techniques of density gradient centrifugation, DEAE cellulose chromatography, and affinity chromatography. A stable 4000-fold purified preparation was obtained as the result of this procedure, yielding 2 bands on acrylamide gel electrophoresis in the presence or absence of sodium dodecyl sulfate (SDS). Molecular weight determinations on calibrated gel columns give a value of 95, 000 in the absence and about 50, 000 in the presence of SDS, indicating a monomer-dimer relationship.