What role does apoC-II play in lipoprotein metabolism?

ApoC-II plays a crucial role in lipoprotein metabolism by activating peripheral lipoprotein lipase (LPL). LPL is an enzyme located on the endothelial surface of capillaries that hydrolyzes triglycerides in lipoproteins into free fatty acids and glycerol. When lipoproteins such as chylomicrons and VLDL (very low-density lipoproteins) enter the bloodstream, the presence of apoC-II on their surface is essential for the activation of LPL.

This activation facilitates the breakdown of triglycerides, allowing the release of fatty acids, which can then be taken up by peripheral tissues for energy use or storage. Without adequate apoC-II, LPL would remain inactive, leading to impaired fat metabolism and elevated triglyceride levels in the bloodstream.

The other options discuss functions not directly associated with apoC-II. For instance, apoC-II does not inhibit lipase activity; rather, it is essential for stimulating it. It also does not play a direct role in the formation of HDL or in cholesterol binding within tissues. These points clarify why the role of apoC-II as an activator of peripheral lipoprotein lipase is so critical in lipid metabolism.