Regulation of Human Plasma Lecithin:cholesterol Acyltransferase Activity by Lipoprotein Acceptor Cholesteryl Ester Content

Very low density lipoproteins and low density lipoproteins attain maximal cholesteryl ester contents during the incubation of human plasma and, under these conditions, both lecithin:cholesterol acyltransferase and transfer proteins are inhibited. These lipoproteins provide the major part of free cholesterol for the lecithin:cholesterol acyltransferase reaction, and are the major acceptors of cholesteryl ester generated by lecithin:cholesterol acyltransferase and transported to the lipoprotein acceptors by the transfer protein. The results obtained indicate that the concentration of acceptor limits esterification and transfer in plasma, and that in vivo these acceptors contain close to their maximal cholesteryl ester content. Human plasma end product acceptor lipoproteins have a composition similar to that of the ester-rich large low density lipoprotein characteristic of primate models of experimental atherosclerosis.