Statin drugs block the enzyme responsible for cholesterol production in the liver. Which enzyme is inhibited by statins?

• A. HMG-CoA reductase
• B. Amylase
• C. Lipase
• D. Acetyl-CoA carboxylase

Answer: (A)

Statins work by blocking the liver’s production of cholesterol through inhibiting an enzyme that catalyzes the first committed step in cholesterol synthesis: HMG-CoA reductase. This enzyme converts HMG-CoA to mevalonate, a key precursor in cholesterol formation. Because this step is rate-limiting, inhibiting it lowers hepatic cholesterol synthesis, prompting the liver to upregulate LDL receptors and pull more LDL from the blood, reducing plasma LDL cholesterol. The other enzymes listed are involved in different processes—amylase digests starch, lipase digests fats, and acetyl-CoA carboxylase is for fatty acid synthesis—not cholesterol—and are not targeted by statins.