MCQ – 136673

Which of the following enzymes is dependent on Vitamin C for its activity?

Correct Answer � C Explanation

Prolyl Hydroxylase

• Prolyl hydroxylase is a key enzyme involved in collagen synthesis.

• It hydroxylates proline residues in procollagen, an essential step that stabilizes the collagen triple helix via hydrogen bonding.

• This enzyme requires Vitamin C (ascorbic acid) as a cofactor to maintain its iron in the ferrous (Fe²⁺) state during the hydroxylation reaction.

• Vitamin C deficiency (as in scurvy) leads to defective collagen formation, resulting in symptoms like bleeding gums, poor wound healing, and fragile capillaries.

Why Other Options Are Incorrect:

A. Lysyl Dehydrogenase

• Not a recognized enzyme in collagen biosynthesis or Vitamin C metabolism. Possibly a distractor or misnomer.

B. Lysyl Oxidase

• Involved in cross-linking of collagen and elastin fibers in the extracellular matrix.

• Requires copper as a cofactor, not Vitamin C.

• Deficiency causes connective tissue disorders (e.g., Menkes disease), but not related to ascorbic acid.

D. Hydroxyprolyl Kinase

• Not a standard enzyme in collagen or connective tissue metabolism.

• Likely a distractor with no established physiological role or vitamin dependency.