Question

Regarding apoprotein-C, which of the following is true?

• A. Activates lipoprotein lipase
• B. Inactivates lipoprotein lipase
• C. Facilitates triglyceride transport
• D. All of the above

Hint:

Apo C-II activates LPL, apo C-III inhibits it, and apo C rides on triglyceride-rich lipoproteins.

Answer 1

The Correct Option is D

Step 1: Treat apoprotein C as a family rather than a single molecule. Its members ride on triglyceride-rich lipoproteins and each tunes the activity of lipoprotein lipase differently.

Step 2: One member, apo C-II, switches lipoprotein lipase on, which is required for clearing triglycerides from chylomicrons and VLDL. A different member, apo C-III, does the opposite and damps lipoprotein lipase down. So both an activating and an inactivating action are represented within apo C.

Step 3: Beyond enzyme control, apo C is a built-in part of chylomicrons and VLDL. Being incorporated into these carriers, it helps shuttle triglycerides through the circulation.

Step 4: Because activation of lipoprotein lipase, inactivation of lipoprotein lipase, and facilitation of triglyceride transport are all attributable to apo C subtypes, every listed statement holds true.

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