Galactonolactone dehydrogenase explained

L-galactonolactone dehydrogenase
Ec Number:	1.3.2.3
Cas Number:	2603847

L-galactonolactone dehydrogenase (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 plants and other photosynthetic eukaryotes.^[6]

Notes and References

1. Properties of partially purified L-galactono-γ-lactone dehydrogenase . Mapson, L.W. . Breslow, E. . Biochem. J. . 1957 . 65 . 29 .
2. Mapson LW, Isherwood FA, Chen YT . Biological synthesis of L-ascorbic acid: the conversion of L-galactono-gamma-lactone into L-ascorbic acid by plant mitochondria . The Biochemical Journal . 56 . 1 . 21–8 . January 1954 . 13126087 . 1269564 . 10.1042/bj0560021 .
3. Isherwood FA, Chen YT, Mapson LW . Synthesis of L-ascorbic acid in plants and animals . The Biochemical Journal . 56 . 1 . 1–15 . January 1954 . 13126085 . 1269562 . 10.1042/bj0560001 .
4. Oba K, Ishikawa S, Nishikawa M, Mizuno H, Yamamoto T . Purification and properties of L-galactono-gamma-lactone dehydrogenase, a key enzyme for ascorbic acid biosynthesis, from sweet potato roots . Journal of Biochemistry . 117 . 1 . 120–4 . January 1995 . 7775377 . 10.1093/oxfordjournals.jbchem.a124697 .
5. Ostergaard J, Persiau G, Davey MW, Bauw G, Van Montagu M . Isolation of a cDNA coding for L-galactono-gamma-lactone dehydrogenase, an enzyme involved in the biosynthesis of ascorbic acid in plants. Purification, characterization, cDNA cloning, and expression in yeast . The Journal of Biological Chemistry . 272 . 48 . 30009–16 . November 1997 . 9374475 . 10.1074/jbc.272.48.30009 . free .
6. Wheeler G, Ishikawa T, Pornsaksit V, Smirnoff N . Evolution of alternative biosynthetic pathways for vitamin C following plastid acquisition in photosynthetic eukaryotes . eLife . 4 . March 2015 . 25768426 . 4396506 . 10.7554/eLife.06369 . free .