A 55-year-old alcoholic with chronic liver disease presents with ophthalmoplegia, ataxia, and confusion. He is treated with intravenous thiamine. Thiamine pyrophosphate (TPP) is a cofactor for four enzyme complexes. Which is NOT one of them?
- A Phosphoglucose isomerase ✓
- B Pyruvate dehydrogenase complex
- C α-ketoglutarate dehydrogenase complex
- D Transketolase
Correct answer: A. Phosphoglucose isomerase
Explanation
TPP (thiamine pyrophosphate) is required by: pyruvate dehydrogenase (converts pyruvate to acetyl-CoA), α-ketoglutarate dehydrogenase (TCA cycle), branched-chain α-ketoacid dehydrogenase (BCKAD, for MSUD), and transketolase (HMP shunt). Phosphoglucose isomerase (converts glucose-6-phosphate to fructose-6-phosphate) requires no cofactor other than zinc and does not involve a carbon-carbon bond lysis/formation requiring TPP. Transketolase assay with and without TPP addition is a classic lab test for thiamine deficiency status.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.