incorygible
Posts: 374
Joined: Feb. 2006
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| Quote (Henry J @ May 17 2006,11:41) | Re "Fish, on the other hand, are missing more than just GULO (as shown in that study I pointed out). "
Is that all fish, or just some of them?
Henry |
Good question. Only stuff I've seen on ascorbate in fish pertains to transgenic salmon, and suggests that an inability to synthesize vitamin C endogenously is common to all teleost fish (their dietary requirements are also far lower than mammals, and deficiency is not as severe). Non-dietary GLO has, however, been found in lower fish. Looking into it a little further, it appears that there is a bit of controversy as to whether any teleosts can synthesize vitamin C, and one interesting study suggests mullet may be able to biosynthesize GLO seasonally. The Krasnov et al. (1998) paper began with the hypothesis that GLO is the only thing missing in vitamin C synthesis (since biochemical precursors to GLO are present in tissues). However, they concluded that:
| Quote | | Probably, the conditions required for the efficient translation, posttranslational modification and compartmentalization of GLO, which have been conserved in guinea pigs after loss of their own gene, are absent from rainbow trout cells. However, considering the long evolutionary distance between mammals and fish, it is possible that transfer of a GLO gene from lower fish could be more probable for correction of L-ascorbic acid biosynthesis. |
(Hey, Dave, did you catch that useful, practical evolutionary prediction at the end there?)
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