Malonyl-CoA is a potent inhibitor of which enzyme, thereby coordinating de novo fatty acid synthesis with mitochondrial beta-oxidation to prevent a futile cycle?

• A Acetyl-CoA carboxylase
• B Carnitine palmitoyltransferase I (CPT-I) ✓
• C HMG-CoA synthase (mitochondrial)
• D Fatty acid synthase (FAS)

Explanation

Malonyl-CoA, the product of the committed rate-limiting step of fatty acid synthesis (catalyzed by acetyl-CoA carboxylase), inhibits CPT-I, the enzyme that transfers long-chain fatty acyl groups onto carnitine for transport into mitochondria for beta-oxidation. This ensures that when fatty acid synthesis is active (fed state), concurrent beta-oxidation is suppressed, avoiding a futile cycle. During fasting, malonyl-CoA levels fall, relieving CPT-I inhibition.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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