13. Discussion

  • Ascorbic acid serves as a common reductant/cofactor in many enzymatic reactions (especially those requiring reduced Fe2+).
    1) Carnitine Synthesis
    2) Catecholamine Synthesis
    3) Peptide Hormone Synthesis
    4) Tyrosine Metabolism
    5) Generic Antioxidant
    6) Role in Immune Function?
  • The critical functional role is to serve as a cofactor for protocollagen hydroxylase, the enzyme responsible for hydroxylation of the prolyl and lysyl residues in collagen.
  • The triple-helix structure of mature collagen is markedly stabilized by hydroxylation (Tm of 24 ºC vs. 58 ºC) as it allows the formation of a water-mediated hydrogen bond between collagen strands.
  • By an independent mechanism, the synthesis of proteoglycans and protocollagen is decreased in ascorbic acid deficiency (inhibition of insulin-like growth factor I?).