Maple syrup urine disease (MSUD) results from deficiency of branched-chain alpha-keto acid dehydrogenase (BCKAD). The toxic accumulating metabolites are:

• A Phenylalanine and phenylpyruvate
• B Homocysteine and methionine
• C Propionyl-CoA and methylmalonyl-CoA
• D Leucine, isoleucine, and valine along with their respective keto acids ✓

Explanation

BCKAD catalyses oxidative decarboxylation of branched-chain keto acids (alpha-ketoisocaproate from leucine, alpha-keto-beta-methylvalerate from isoleucine, alpha-ketoisovalerate from valine); deficiency causes accumulation of all three BCAAs and their corresponding keto acids, which are neurotoxic and produce the characteristic sweet maple syrup odour in urine. Phenylalanine/phenylpyruvate accumulate in PKU. Homocysteine/methionine in CBS deficiency. Propionyl/methylmalonyl-CoA in propionic and methylmalonic acidaemia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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