L-gulonolactone oxidase
From Wikipedia, the free encyclopedia
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gulonolactone (L-) oxidase pseudogene
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| Identifiers | |
| Symbol | GULOP |
| Entrez | 2989 |
| HUGO | 4695 |
| OMIM | 240400 |
| RefSeq | NG_001136 |
| Other data | |
| EC number | 1.1.3.8 |
| Locus | Chr. 8 p21.1 |
L-gulonolactone oxidase (EC 1.1.3.8) is an enzyme that catalyzes the reaction of D-glucuronolactone (also known as L-gulono-1,4-lactone) with oxygen to L-xylo-hex-3-gulonolactone and hydrogen peroxide. It uses FAD as a cofactor. The L-xylo-hex-3-gulonolactone (2-keto-gulono-gamma-lactone) is able to spontanously convert to hexuronic acid (ascorbic acid), without enzymatic action.
The CAS number for this enzyme is 9028-78-8
[edit] Gulonolactone oxidase deficiency
The non-functional gulonolactone oxidase pseudogene (GULOP) was mapped to human chromosome 8p21 that corresponds to an evolutionarily conserved segment on either porcine chromosome 4 (SSC4) or 14 (SSC14).[1] GULO produces the precursor to ascorbic acid, which spontaneously converts to the vitamin ("vitamin C").
The loss of activity of the gene for L-gulonolactone oxidase (GULO) has occurred separately in the history of several species. The loss of this enzyme activity is responsible of inability of guinea pigs to enzymatically synthesize vitamin C, but this event happened independently of the loss in the haplorrhini suborder of primates, including humans. The remains of this non-functional gene with many mutations, is however still present in the genome of the guinea pigs and in humans.[2][3] The function of GULO appears to have been lost several times, and possibly re-acquired, in several lines of passerine birds, where ability to make vitamin C varies from species to species. In addition, GULO activity has also been lost in all types of bats, regardless of diet.[4]
Loss of GULO activity in the primate order occurred about 63 million years ago, at about the time it split into the suborders haplorrhini (which lost the enzyme activity) and the more primitive strepsirrhini (which retained it). The haplorrhini ("simple nosed") primates, which cannot make vitamin C enzymatically, include the tarsiers and the simians (apes, monkeys and humans). The suborder strepsirrhini (bent or wet nosed prosimians) which are still able to make vitamin C enzymatically, include lorises, galagos, pottos, and to some extent, lemurs. [5].
L-gulonolactone oxidase deficiency is called "hypoascorbemia"[6] and is described by OMIM (Online Mendelian Inheritance in Man)[7] as "a public inborn error of metabolism", as it affects all humans. There exists a wide discrepancy between the amounts of ascorbic acid other primates consume and what is recommended as "reference intakes" for humans.[8]
[edit] References
- ^ GULOP - iHOP
- ^ J Biol. Chem. 1992 PMID 1400507
- ^ Random nucleotide substitutions in primate nonfunctional gene for L-gulono-gamma-lactone oxidase, the missing enzyme in L-ascorbic acid biosynthesis. Biochim Biophys Acta. 1999 PMID 10572964
- ^ Can passerines synthesize vitamin C? Carlos Martinez del Rio. The Auk, July, 1997. [1]
- ^ Am J Phys Anthropol. 1987 May;73(1):65-70. Vitamin C biosynthesis in prosimians: evidence for the anthropoid affinity of Tarsius. Pollock JI, Mullin RJ. PMID 3113259
- ^ HYPOASCORBEMIA - NCBI
- ^ OMIM - Online Mendelian Inheritance in Man - NCBI
- ^ Micronutrient intakes of wild primates: are humans different?. Retrieved on 2007-03-11.
[edit] See also
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