Ascorbate regeneration by the reduced form of 2-amino-3-carboxy-1,4-naphthoquinone, a strong growth stimulator for bifidobacteria

Citation
S. Yamazaki et al., Ascorbate regeneration by the reduced form of 2-amino-3-carboxy-1,4-naphthoquinone, a strong growth stimulator for bifidobacteria, J AGR FOOD, 48(11), 2000, pp. 5643-5648
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Agricultural Chemistry","Chemistry & Analysis
Journal title
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
ISSN journal
0021-8561 → ACNP
Volume
48
Issue
11
Year of publication
2000
Pages
5643 - 5648
Database
ISI
SICI code
0021-8561(200011)48:11<5643:ARBTRF>2.0.ZU;2-G
Abstract
Nonenzymatic reduction of dehydroascorbate into ascorbate by the reduced fo rm (quinol form) of 2-amino-3-carboxy-1,4-naphthoquinone, a strong growth s timulator for bifidobacteria, has been found. The bimolecular reaction rate constant was evaluated as 9 M-1 s(-1) at pH 7.0. This reaction has been su ccessfully coupled with enzymatic regeneration of the naphthoquinol by NAD( P)H in cell free extracts of Bifidobacterium longum 6001. The overall react ion is a regeneration of NAD(P)(+) by dehydroascorbate for a regeneration o f ascorbate by NAD(P)H], in which the naphthoquinone/quino1 redox couple fu nctions as an electron transfer mediator. Kinetic study of the reduction of dehydroascorbate with related quinol compounds suggested the significance of the amino substituent of the naphthoquinol. A mechanism of the electron transfer from the quinol to dehydroascorbate is proposed, where the first s tep of the reaction is a nucleophilic addition of the C(2)-amino substituen t of the naphthoquinol to the C(2)-position of dehydroascorbate to form a S chiff base intermediate.