Lecithin:cholesterol acyltransferase (LCAT) is a glycoprotein of 416 residues, synthesized almost exclusively in the liver and secreted into plasma, where it circulates bound to High Density Lipoproteins (HDL) (1). The plasma concentration of LCAT in humans (about 5 mg/L) varies little with gender, age, alimentary habits, and smoking.
75% of cholesterol in plasma is in the esterified form, and most of it originates from the LCAT reaction. LCAT catalyzes the transfer of the sn-2 fatty acid of lecithin to the free 3-OH group of cholesterol, generating esterified cholesterol and lysolecithin. HDL cholesterol is the preferred substrate for LCAT, and apolipoprotein A-I, the major HDL protein, acts as a cofactor in the reaction (1). Through this reaction LCAT plays a major role in the maturation of HDL, and contributes to the determination of HDL composition, structure, intravascular metabolism, and plasma concentration (1).