A malnourished elderly patient with poor dietary intake shows delayed wound healing with defective collagen cross-linking. Which biochemical step of collagen synthesis is directly dependent on adequate vitamin C availability?

• A Formation of the peptide bonds linking glycine residues
• B Hydroxylation of proline and lysine residues in procollagen ✓
• C Glycosylation of the terminal propeptides
• D Cleavage of procollagen to tropocollagen by procollagen peptidase

Explanation

Vitamin C is a required cofactor for prolyl and lysyl hydroxylases, enzymes that hydroxylate proline and lysine in procollagen. Hydroxylated residues permit stable hydrogen bonding and formation of the mature triple helix. In deficiency the triple helix is unstable, collagen secretion is impaired, and healing fails, the same defect seen in scurvy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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