Biotin deficiency presents with alopecia, dermatitis, and neurological symptoms. The biochemical reason is impairment of which enzymatic reactions?

• A Biotin is a cofactor for transketolase; deficiency impairs the pentose phosphate pathway
• B Biotin deficiency impairs coenzyme A synthesis, affecting all acyl-CoA-dependent reactions
• C Biotin is required for disulfide bond formation in keratin, causing hair and nail changes
• D Biotin is a CO2 carrier for carboxylase enzymes including acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, and beta-methylcrotonyl-CoA carboxylase ✓

Explanation

Biotin serves as a prosthetic group (covalently bound via lysine) for four mitochondrial carboxylase enzymes in humans: pyruvate carboxylase (gluconeogenesis), acetyl-CoA carboxylase (fatty acid synthesis), propionyl-CoA carboxylase (odd-chain FA, branched-chain AA catabolism), and beta-methylcrotonyl-CoA carboxylase (leucine catabolism). Biotin deficiency is rare — usually caused by raw egg white consumption (avidin binds biotin) or prolonged TPN. Multiple carboxylase deficiency from holocarboxylase synthetase deficiency mimics biotin deficiency.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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