Galactonolactone dehydrogenase

L-galactonolactone dehydrogenase (EC 1.3.2.3, galactonolactone dehydrogenase, L-galactono-gamma-lactone dehydrogenase, L-galactono-gamma-lactone:ferricytochrome-c oxidoreductase, GLDHase, GLDase) is an enzyme with systematic name L-galactono-1,4-lactone:ferricytochrome-c oxidoreductase.^[1]^[2]^[3]^[4]^[5] This enzyme catalyses the following chemical reaction

(1) L-galactono-1,4-lactone + 2 ferricytochrome c

\rightleftharpoons

L-ascorbate + 2 ferrocytochrome c + 2 H⁺

(2) L-ascorbate + 2 ferricytochrome c

\rightleftharpoons

L-dehydroascorbate + 2 ferrocytochrome c + 2 H⁺ (spontaneous)

This enzyme catalyses the final step in the biosynthesis of L-ascorbic acid in higher plants and in nearly all higher animals, except for primates and some birds.

References

↑ Mapson, L.W. and Breslow, E. (1957). "Properties of partially purified L-galactono-γ-lactone dehydrogenase". Biochem. J. 65: 29–29.
↑ Mapson, L.W., Isherwood, F.A. and Chen, Y.T. (1954). "Biological synthesis of L-ascorbic acid: the conversion of L-galactono-γ-lactone into L-ascorbic acid by plant mitochondria". Biochem. J. 56 (1): 21–28. PMC 1269564. PMID 13126087.
↑ Isherwood, F.A., Chen, Y.T. and Mapson, L.W. (1954). "Synthesis of L-ascorbic acid in plants and animals.". Biochem. J. 56 (1): 1–15. PMC 1269562. PMID 13126085.
↑ Ôba, K., Ishikawa, S., Nishikawa, M., Mizuno, H. and Yamamoto, T. (1995). "Purification and properties of L-galactono-γ-lactone dehydrogenase, a key enzyme for ascorbic acid biosynthesis, from sweet potato roots". J. Biochem. (Tokyo) 117 (1): 120–124. PMID 7775377.
↑ Østergaard, J., Persiau, G., Davey, M.W., Bauw, G. and Van Montagu, M. (1997). "Isolation of a cDNA coding for L-galactono-γ-lactone dehydrogenase, an enzyme involved in the biosynthesis of ascorbic acid in plants. Purification, characterization, cDNA cloning, and expression in yeast". J. Biol. Chem. 272 (48): 30009–30016. doi:10.1074/jbc.272.48.30009. PMID 9374475.

External links

L-galactonolactone dehydrogenase at the US National Library of Medicine Medical Subject Headings (MeSH)

Oxidoreductases: CH–CH oxidoreductases (EC 1.3)

1.3.1: NAD/NADP acceptor	Enoyl-acyl carrier protein reductase/Enoyl ACP reductase 7-Dehydrocholesterol reductase Biliverdin reductase 2,4 Dienoyl-CoA reductase Dihydroxymethyloxo-tetrahydroquinoline dehydrogenase

1.3.3: Oxygen acceptor	Dihydroorotate dehydrogenase Coproporphyrinogen III oxidase Protoporphyrinogen oxidase Bilirubin oxidase Acyl-CoA oxidase Dihydrouracil oxidase Tetrahydroberberine oxidase Secologanin synthase Tryptophan alpha,beta-oxidase Pyrroloquinoline-quinone synthase L-galactonolactone oxidase

1.3.5: Quinone	Succinate dehydrogenase SDHA SDHB SDHC SDHD

1.3.99: Other acceptors	Fumarate reductase Butyryl-CoA dehydrogenase Acyl CoA dehydrogenase ACADSB ACADS 5α-reductase SRD5A1 SRD5A2 SRD5A3 Glutaryl-CoA dehydrogenase Isovaleryl coenzyme A dehydrogenase 3-oxo-5beta-steroid 4-dehydrogenase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases(list) EC2 Transferases(list) EC3 Hydrolases(list) EC4 Lyases(list) EC5 Isomerases(list) EC6 Ligases(list)

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