A chronic alcoholic presents with Wernicke's encephalopathy (confusion, ophthalmoplegia, ataxia). The biochemical basis is deficiency of thiamine (B1) required as TPP for three key enzyme complexes. Which of the following enzymes does NOT require TPP?

• A Pyruvate dehydrogenase complex
• B Alpha-ketoglutarate dehydrogenase complex
• C Branched-chain alpha-keto acid dehydrogenase (BCKDH)
• D Succinate dehydrogenase ✓

Explanation

Succinate dehydrogenase (complex II of the ETC) requires FAD (covalently bound) as its cofactor; it does not require TPP. The three major TPP-dependent dehydrogenase complexes are: pyruvate dehydrogenase, alpha-ketoglutarate (2-oxoglutarate) dehydrogenase, and BCKDH. Additionally, transketolase (HMP shunt) requires TPP. Succinate dehydrogenase also does not use a classic cofactor vitamin; its FAD is supplied by riboflavin (B2).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.