Which set of enzymes is involved in interconversion of mature alpha-HDL subspecies?

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

Answer: (A)

HDL particles undergo remodeling by enzymes that change their size and lipid content, allowing interconversion among mature alpha-HDL subspecies. Hepatic lipase and endothelial lipase act on the HDL surface, hydrolyzing phospholipids and triglycerides to trim the particle and shift it between larger (HDL2) and smaller (HDL3) mature forms. Lecithin-cholesterol acyltransferase then esterifies free cholesterol on HDL, promoting maturation and stabilizing the particle as it remodels. Together, these three enzymes drive the dynamic remodeling of mature HDL subspecies. Lipoprotein lipase mainly targets triglyceride-rich lipoproteins and influences HDL only indirectly, while CETP mediates lipid exchange between lipoproteins rather than directly remodeling mature HDL. Hence, hepatic lipase, endothelial lipase, and LCAT best explain interconversion among mature alpha-HDL subspecies.