A 65-year-old man with a history of poor diet presents with perifollicular hemorrhages, gingival bleeding, corkscrew hairs, and poor wound healing. Biochemically, scurvy results from impaired hydroxylation of specific amino acid residues during collagen synthesis. Which amino acid residues require vitamin C as a cofactor for hydroxylation?

• A Proline and lysine ✓
• B Glutamate and aspartate
• C Glycine and alanine
• D Cysteine and methionine

Explanation

Vitamin C is an essential cofactor for prolyl hydroxylase and lysyl hydroxylase, enzymes that hydroxylate proline and lysine residues in procollagen. This hydroxylation is required for stable triple-helix formation. Without it, collagen is weak, leading to the vascular and cutaneous manifestations of scurvy. The most tempting distractor confuses this with vitamin K-dependent gamma-carboxylation of glutamate residues.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.