The plasma lecithin:cholesterol acyltransferase reaction

TLDR

Evidence supports a plasma lecithin‑cholesterol acyltransferase that acts on lipid reactants and lipoprotein substrates, yet prior studies rarely separate enzyme from substrate effects. The study proposes that LCAT may facilitate cholesterol transport from peripheral tissues to the liver. Incubation of plasma with radiolabeled cholesterol shows that all major lipoproteins esterify, but high‑density lipoproteins are preferential substrates. Reduced liver function or evisceration lowers cholesterol esterification, indicating hepatic regulation of LCAT and its substrates, and the reaction is the main source of plasma esterified cholesterol with possible broader extracellular roles.

Abstract

Evidence for the existence of a plasma lecithin : cholesterol acyltransferase is reviewed with emphasis not only on the lipid reactants, but also on the lipoprotein substrates and products. The cholesteryl esters of all major lipoprotein classes become labeled when plasma is incubated with cholesterol-(14)C. However, the smaller, lecithin-rich high density lipoproteins appear to be preferred substrates. Most studies of factors that influence the acyltransferase reaction have not adequately distinguished between effects on the enzyme and effects on the lipoprotein substrates. However, the fact that cholesterol esterification is diminished in plasma from eviscerated animals or from patients with reduced liver function suggests that the liver may regulate both the level of the enzyme and that of the substrates. Several indications exist that the acyltransferase reaction is the major source of plasma esterified cholesterol in man. Furthermore, the reaction may have a broader, extracellular function. One possibility is that it plays a role in the transport of cholesterol from peripheral tissues to the liver.