Which enzyme esterifies free cholesterol inside nascent pre-B HDL to form mature alpha-HDL?

• A. LCAT
• B. CETP
• C. Hepatic Lipase
• D. Endothelial Lipase

Answer: (A)

Esterification of free cholesterol inside nascent pre-beta HDL to form mature alpha-HDL is driven by LCAT. Lecithin-cholesterol acyltransferase is secreted by the liver and activated by apoA-I on HDL. It uses phosphatidylcholine (lecithin) as the acyl donor to convert free cholesterol into cholesteryl esters, which are hydrophobic and migrate to the HDL core. This core enrichment converts the discoidal nascent HDL into the spherical mature HDL particle, increasing its size and shifting its mobility to the alpha region. While other enzymes remodel HDL—CETP transfers cholesteryl esters between lipoproteins, and hepatic or endothelial lipases hydrolyze triglycerides and phospholipids—none esterify cholesterol within nascent HDL, so they don’t drive the maturation step.