Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Imai, T. et al.

Imai, Karita, Shiratori, Hattori, Nunome, Oba, Hirai,

L-galactono-gamma-lactone dehydrogenase from sweet potato: purification and cDNA sequence analysis.

L-Galactono-gamma-lactone dehydrogenase (EC 1.3.2.3, GLDHase) was partially purified from mitochondria of sweet potato tuberous roots over 600-fold on a specific activity basis, followed by purification of the enzyme protein of 56 kDa by a preparative SDS-PAGE. The absorption spectrum of the hydroxylapatite column-purified GLDH-ase showed peaks at 448 and 373 nm, suggesting the presence of flavin as a prosthetic group. The activity of GLDH-ase was inhibited by lycorine, an alkaloid which inhibits ascorbic acid biosynthesis in vivo. N-terminal partial sequences of four internal polypeptides generated by partial digestion of GLDHase with V8 protease were determined. The deduced nucleotide sequences were used to amplify a cDNA fragment of the GLDHase gene. The clone encoded a polypeptide of 581 amino acid residues with a molecular mass of 66 kDa. The deduced amino acid sequence showed 77% identity with that of cauliflower GLDHase, and significant homology to those of L-gulono-gamma-lactone oxidase (22% identity) from rat and L-galactono-gamma-lactone oxidase from yeast (17% identity), which are enzymes involved in L-ascorbic acid biosynthesis in these organisms. The absorption spectrum and cDNA sequence suggested that the flavin group bound noncovalently. We conclude that GLDHase, L-gulono-gamma-lactone oxidase and L-galactono-gamma-lactone oxidase are homologous in spite of the difference in substrates and electron acceptors. Genomic Southern analysis suggested that GLDHase gene exists as a single copy in the genome of sweet potato.[1]

References

L-galactono-gamma-lactone dehydrogenase from sweet potato: purification and cDNA sequence analysis. Imai, T., Karita, S., Shiratori, G., Hattori, M., Nunome, T., Oba, K., Hirai, M. Plant Cell Physiol. (1998) [Pubmed]

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