Biotin serves as a CO2 carrier in carboxylase reactions. Which of the following enzymes does NOT require biotin?

• A Pyruvate carboxylase
• B Acetyl-CoA carboxylase
• C Pyruvate dehydrogenase ✓
• D Propionyl-CoA carboxylase

Explanation

Biotin is the prosthetic group of four mammalian carboxylases: pyruvate carboxylase (oxaloacetate synthesis), acetyl-CoA carboxylase (malonyl-CoA synthesis for fatty acid synthesis), propionyl-CoA carboxylase (methylmalonyl-CoA synthesis), and 3-methylcrotonyl-CoA carboxylase (leucine catabolism). Pyruvate dehydrogenase (PDH) is an alpha-keto acid dehydrogenase complex requiring TPP, lipoic acid, CoA, FAD and NAD+ — it does not require biotin. PDH converts pyruvate to acetyl-CoA (with CO2 release as decarboxylation, not carboxylation). Biotin deficiency causes defects in all four carboxylase reactions, presenting with dermatitis, alopecia, ataxia and organic aciduria.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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