Where do LDL particles interact with lipoprotein lipase to release fatty acids?

• A. In the lumen of the artery; lipoprotein lipase acts there.
• B. Within the endothelium; cholesteryl ester transfer protein.
• C. In the plasma; hepatic lipase acts on LDL.
• D. In the sub-endothelial space, LDL is trapped and lipoprotein lipase hydrolyzes fatty acids from VLDL.

Answer: (D)

Lipoprotein lipase works on triglyceride-rich lipoproteins at the endothelial surface, releasing fatty acids that nearby tissues can take up. In arteries, this activity occurs near the subendothelial space where LDL can become trapped in the arterial wall. The best option captures both ideas: LPL acts to hydrolyze fatty acids from VLDL in that subendothelial region where LDL is retained. LDL itself isn’t a substrate for LPL, and CETP or hepatic lipase aren’t the enzymes described here.