A 48-year-old man with a history of poor nutrition and chronic alcohol use presents with perifollicular hemorrhages, corkscrew hairs, and bleeding gums. Which enzymatic reaction is directly impaired by the deficient vitamin in this condition?

• A Carboxylation of prothrombin
• B Methylation of homocysteine
• C Decarboxylation of glutamic acid
• D Hydroxylation of proline residues in collagen ✓

Explanation

This patient has scurvy from vitamin C deficiency. Vitamin C is a cofactor for prolyl hydroxylase and lysyl hydroxylase, which hydroxylate proline and lysine residues during collagen synthesis. Without hydroxylation, collagen triple helix stability fails, causing fragile blood vessels. Carboxylation of prothrombin requires vitamin K, not vitamin C.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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