A farmer presents after accidental ingestion of rodenticide containing sodium fluoroacetate ('1080'). The toxin is converted to fluorocitrate, which potently inhibits which enzyme of the TCA cycle?

• A Citrate synthase
• B Succinyl-CoA synthetase
• C Isocitrate dehydrogenase
• D Aconitase ✓

Explanation

Fluoroacetate is converted to fluoroacetyl-CoA, which condenses with oxaloacetate to form fluorocitrate, a potent competitive inhibitor of aconitase. This blocks the conversion of citrate to isocitrate, causing citrate accumulation and shutdown of the cycle. Isocitrate dehydrogenase is the rate-limiting regulatory step but is not the target here, and citrate synthase remains active, which is why citrate builds up.

Reference: Harper's Illustrated Biochemistry, 31st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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