Statin drugs are inhibitors of which enzyme?

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

Answer: (A)

Statins work by inhibiting the enzyme that catalyzes the rate-limiting step in cholesterol synthesis, HMG-CoA reductase. This enzyme converts HMG-CoA to mevalonate in the liver, a pivotal early step in making cholesterol. Blocking this step lowers hepatic cholesterol production, which prompts more LDL receptors on liver cells to be expressed and pull LDL cholesterol out of the bloodstream, reducing plasma LDL levels. This mechanism is specific to cholesterol biosynthesis. Amylase and lipase are digestive enzymes for carbohydrates and fats, respectively, and acetyl-CoA carboxylase is involved in fatty acid synthesis but is not the target of statins.