Question

Statins produced by Monascus purpureus have been used as blood-cholesterol lowering agents.

How do statins lower the blood-cholesterol levels in the body?

• A. They cause the breakdown of the cholesterol molecules
• B. They eliminate chloesterol from the body
• C. They inhibit the synthesis of cholesterol
• D. They dissolve the cholesterol in the body

Answer 1

The correct option is C They inhibit the synthesis of cholesterol

The gradual build-up of cholesterol plaques reduces the lumen size of the artery leading to high blood pressure and finally heart attack.

Statins are produced by the yeast Monascus purpureus. They act to lower blood-cholesterol levels by competitively inhibiting the enzyme which is essential for cholesterol synthesis.

In competitive inhibition, the inhibitor binds to the active site of the enzyme and blocks the binding of the actual substrate. It is called competitive inhibition, as the inhibitor competes with the actual substrate of the enzyme.

Statins are competitive inhibitors of HMG-CoA reductase, a key enzyme of cholesterol biosynthesis. Statins are structural analogues of the actual substrate for this enzyme and compete effectively to inhibit HMG-CoA reductase.

Due to this, the actual substrate required for cholesterol synthesis cannot bind to the enzyme and thus cholesterol is not synthesised.

Thus statins inhibit the synthesis of cholesterol and thereby lower blood cholesterol levels.