Paleo Diet and Paleolithic Diet Questions & Answers

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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."

http://en.wikipedia.org/wiki/Hydroxyproline#Clinical_significance

Can we directly utilize the hydroxyproline and hydroxylysine in gelatine to produce collagen thereby conserving bodily stores of ascorbic acid?

edited May 25 2012 at 6:12

asked May 25 2012 at 4:37

Tim
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	Someone ping a nutritionist. This is a good question. – Tyler F May 25 2012 at 14:47
	Thanks Tyler. I think it's a really important question. – Tim May 25 2012 at 21:33
	Very interesting question! And an answer that seems to weaken the argument for supplementing with gelatin. – Matt May 26 2012 at 0:56
	Hi Matt, I still think gelatin is important to supply lots of the raw material for hydroxylation. As a result of this question I'm going to start supplementing with ascorbic acid. – Tim May 26 2012 at 2:29
	Adequate selenium promotes recycling of ascorbic acid: perfecthealthdiet.com/2010/11/… – Tim May 26 2012 at 12:23

AStar · Accepted Answer · 2012-05-25 17:14:04Z UTC

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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.

answered May 25 2012 at 17:14

AStar
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	Thanks for the comment! It would seem inefficient not to be able to recycle hydroxyproline and hydroxylysine from existing collagen. Why wouldn't this be coded for in the RNA? – Tim May 25 2012 at 22:13
	Our bodies typically code for 20 amino acids. Selenocysteine is the very important 21st amino acid, but it requires, an activator to start the synthesis at the ribosome, an entire enzyme to make the selenocysteine, and more signals to finally bring it back and incorporate it into the protein. This is an extensive amount of work and for whatever reason we stopped at 21. Tweaking that basic framework is how we work around the limitation. Why can't be answered. Check out work of Peter Schultz to see some outrageous examples of expanding the genetic code to include more amino acids – AStar May 29 at 6:49

Amy B. · Answer 2 · 2012-05-25 17:33:45Z UTC

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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.

answered May 25 2012 at 17:33

Amy B.
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Using "primary role" in my question was a bit misleading. I meant that hydroxylation is the largest consumer of ascorbic acid, not that it was the most important use for it. – Tim May 25 2012 at 22:30

Tim · Answer 3 · 2012-05-26 00:11:41Z UTC

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)."

Link

Does Gelatin Intake Reduce Ascorbic Acid Requirements?

3 Answers