Physiology & Biochemistry · patient case question
With this cofactor deficiency, which enzyme will NOT function properly, leading to poor collagen formation?
Patient case: Man with bleeding gums, easy bruising and poor wound healing
Patient: Male, 45 years old
Chief complaint: “My gums bleed a lot.”
Background: Vitamin C deficiency. Depression.
Current findings: Easy bruising, poor wound healing, bone pain. Periodontal disease.
Show answer and explanation
Correct answer: D. Lysyl hydroxylase
- A. Hydrogen peroxidase is not the vitamin C–dependent enzyme of collagen synthesis.
- B. Peptidases cleave peptide bonds and are not vitamin C–dependent.
- C. Lysyl OXIDASE cross-links collagen and elastin but requires COPPER, not vitamin C. This is the intended trap: near-identical name, different cofactor.
- D. CORRECT. Ascorbate is the essential cofactor for PROLYL and LYSYL HYDROXYLASE. Without hydroxylation of proline and lysine residues, the procollagen triple helix cannot form stable cross-links. The result is fragile capillaries, defective connective tissue, haemorrhagic gingiva and impaired wound healing — scurvy.
Note: Watch the pair: lysyl HYDROXYLASE needs vitamin C; lysyl OXIDASE needs copper.
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