Purification and properties of L-galactono-gamma-lactone dehydrogenase, a key enzyme for ascorbic acid biosynthesis, from sweet potato roots

L-Galactono-gamma-lactone dehydrogenase (L-galactono-gamma-lactone:ferricytochrome c oxidoreductase [EC 1.3.2.3], GLDHase) which catalyzes the terminal step in the biosynthesis of L-ascorbic acid (ABA) has been purified from roots of sweet potato (Ipomaea batatas L., cv. Kintoki). Highly purified pr...

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Veröffentlicht in:Journal of biochemistry (Tokyo) 1995, Vol.117 (1), p.120-124
Hauptverfasser: Oba, K, Ishikawa, S, Nishikawa, M, Mizuno, H, Yamamoto, T
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Sprache:eng
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Zusammenfassung:L-Galactono-gamma-lactone dehydrogenase (L-galactono-gamma-lactone:ferricytochrome c oxidoreductase [EC 1.3.2.3], GLDHase) which catalyzes the terminal step in the biosynthesis of L-ascorbic acid (ABA) has been purified from roots of sweet potato (Ipomaea batatas L., cv. Kintoki). Highly purified preparation of the GLDHase was obtained by three column chromatography steps with a recovery of ca. 1%, after solubilization from mitochondria in sweet potato roots. SDS-PAGE exhibited a single band at 56 kDa. In the native state, the apparent molecular mass of the enzyme was 56 kDa, based on a Sephadex G-100 gel filtration. The pI and optimum pH values were 5.8 and 7.9, respectively. The Km value for L-galactono-gamma-lactone was 0.12 mM. Substrate inhibition was obtained at concentrations greater than 4.2 mM. The enzyme was inhibited by p-chloromercuribenzoate (PCMB) and acriflavine, and the inhibition of acriflavine was diminished by the addition of FAD or FMN. The only effective substrate for the GLDase was L-galactono-gamma-lactone.
ISSN:0021-924X
1756-2651
DOI:10.1093/oxfordjournals.jbchem.a124697