Cofactor required for lipoprotein lipase activity is:
**Core Concept**
Lipoprotein lipase (LPL) is an enzyme that plays a crucial role in the regulation of HDL and triglyceride metabolism. It catalyzes the hydrolysis of triglycerides in very-low-density lipoproteins (VLDL) and chylomicrons to produce free fatty acids and glycerol.
**Why the Correct Answer is Right**
The activity of lipoprotein lipase is dependent on the presence of a specific cofactor, which is apolipoprotein C-II (apoC-II). ApoC-II binds to the LPL enzyme, facilitating its interaction with the triglyceride-rich lipoproteins and enhancing its catalytic activity. This results in the efficient breakdown of triglycerides, leading to the reduction of circulating triglyceride levels and the elevation of HDL cholesterol.
**Why Each Wrong Option is Incorrect**
* **Option A:** Apolipoprotein A-I (apoA-I) is a major component of HDL and serves as a cofactor for lecithin-cholesterol acyltransferase (LCAT), but it is not involved in lipoprotein lipase activity.
* **Option B:** Apolipoprotein B-100 (apoB-100) is a primary apolipoprotein of LDL and is involved in the regulation of lipoprotein metabolism, but it is not a cofactor for LPL.
* **Option C:** Apolipoprotein E (apoE) plays a role in the clearance of triglyceride-rich lipoproteins from the circulation, but it is not a cofactor for LPL.
**Clinical Pearl / High-Yield Fact**
A deficiency in apoC-II can lead to severe hypertriglyceridemia, a condition characterized by elevated levels of triglycerides in the blood, which can increase the risk of pancreatitis.
**Correct Answer: C. Apolipoprotein C-II. Apolipoprotein C-II (apoC-II).**