Interaction of rat lecithin-cholesterol acyltransferase with rat apolipoprotein A-I and with lecithin-cholesterol vesicles

The interaction of rat plasma lecithin-cholesterol Acyltransferase with lecithin-cholesterol vesicles and with rat apo-A-I was studied in comparison with that of human plasma lecithin-cholesterol Acyltransferase to clarify the reaction mechanism of rat plasma lecithin-cholesterol Acyltransferase. The interaction of both human and rat lecithin-cholesterol Acyltransferase with lecithin-cholesterol vesicles was investigated by gel permeation chromatography on Superose 12. Both Enzymes had almost the same affinity to the vesicles. The affinity of rat Enzyme to rat apo-A-I was stronger than that of human Enzyme to human apo-A-I when estimated on the apo-A-I-Sepharose 4B column. When human apo-A-I was added to the human Enzyme/vesicle mixture which contained the enzyme-vesicle complex, the Enzyme was effectively dissociated from the complex. But when rat apo-A-I was added to the rat Enzyme/vesicle mixture, apo-A-I-enzyme-vesicle complex was still recognized by its elution pattern on gel permeation chromatography. This suggests that the mixture of rat Enzyme, rat apo-A-I, and vesicles, which are the major components in the rat lecithin-cholesterol Acyltransferase reaction, forms a stronger complex than do the components of the human reaction.