Ascorbic acid's primary role is as a cofactor in the hydroxylation reaction of proline and lysine for the production of collagen.
"Proline hydroxylation requires ascorbic acid (vitamin C). The most obvious, first effects (gingival and hair problems) of absence of ascorbic acid in humans come from the resulting defect in hydroxylation of proline residues of collagen, with reduced stability of the collagen molecule, causing scurvy."
Can we directly utilize the hydroxyproline and hydroxylysine in gelatine to produce collagen thereby conserving bodily stores of ascorbic acid?
asked byTim_14 (70)
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on May 25, 2012
at 05:14 PM
From a quick look through your wikipedia link, I don't think so. The addition of the hydroxyl group to the proline is a post translational modification done by prolyl hydroxylase. This step occurs after the protein synthesis. The vitamin c is used as a reducing agent for the Iron in the reaction (gives it electrons). The ingested hydroxy amino acids would most likely not be able to get introduced into the protein during its synthesis as they wouldn't be coded for in the RNA.
on May 25, 2012
at 05:33 PM
And let's not forget that collagen formation is not the only role of vitamin C. It's a biggie, yes, but not the only one.
on May 26, 2012
at 12:11 AM
Seems that the answer is no.
"Although 4-hydroxyproline, the proline congener abundant in mammalian species, is structurally similar to proline, its metabolism is distinctly different (2). A critical contributor to the physical structure of organisms, hydrox-yproline is not found in species before the evo-lution of metazoans. Preformed hydroxypro-line is not incorporated into protein presumably because all the triplet codons were occupied (2, 52). Instead, it is formed by the posttransla-tional hydroxylation of proline in proteins (2). Since hydroxyproline is not recycled for pro-tein synthesis, its degradation continues down to 2- and 3-carbon compounds. The degrada-tive pathway, however, shares some of the en-zymes metabolizing proline (103). The ini-tial step is catalyzed by hydroxyproline oxidase (PRODH2), an enzyme encoded by a gene dis-tinct from that for proline oxidase ( PRODH) and with little overlap in substrate utilization (91). In contrast, in the second step of their degradation, hydroxyproline and proline share the same enzyme, i.e., P5C dehydrogenase (103). It is interesting that P5C reductase from animals not only converts P5C back to proline for protein synthesis, but also can reduce OH-P5C to hydroxyproline even though product hydroxyproline is not reused for protein synthe-sis (3). P5C reductase in prokaryotes, however, does not have this activity for OH-P5C (3)."