HMG-CoA reductase is an enzyme that plays a crucial role in the body's cholesterol production. It catalyzes the conversion of HMG-CoA to mevalonate, which is a key step in the biosynthesis of cholesterol and other sterols. This enzyme is primarily found in the liver, where cholesterol is synthesized and regulated. Inhibiting HMG-CoA reductase is the mechanism of action for a class of medications known as statins. These drugs are commonly prescribed to lower cholesterol levels in the blood, thereby reducing the risk of cardiovascular diseases. By blocking this enzyme, statins help to decrease the overall production of cholesterol in the body.