Publications

• Characterization of an l-Ascorbate Catabolic Pathway with Unprecedented Enzymatic Transformations.

  Stack T.M.M., Morrison K.N., Dettmer T.M., Wille B., Kim C., Joyce R., Jermain M., Naing Y.T., Bhatti K., Francisco B.S., Carter M.S., Gerlt J.A.

  l-Ascorbate (vitamin C) is ubiquitous in both our diet and the environment. Here we report that <i>Ralstonia eutropha</i> H16 (<i>Cupriavidus necator</i> ATCC 17699) uses l-ascorbate as sole carbon source via a novel catabolic pathway. RNaseq identified eight candidate catabolic genes, sequence si ... >> More

  l-Ascorbate (vitamin C) is ubiquitous in both our diet and the environment. Here we report that <i>Ralstonia eutropha</i> H16 (<i>Cupriavidus necator</i> ATCC 17699) uses l-ascorbate as sole carbon source via a novel catabolic pathway. RNaseq identified eight candidate catabolic genes, sequence similarity networks, and genome neighborhood networks guided predictions for function of the encoded proteins, and the predictions were confirmed by <i>in vitro</i> assays and <i>in vivo</i> growth phenotypes of gene deletion mutants. l-Ascorbate, a lactone, is oxidized and ring-opened by enzymes in the cytochrome <i>b</i>₅₆₁ and gluconolactonase families, respectively, to form 2,3-diketo-l-gulonate. A protein predicted to have a WD40-like fold catalyzes an unprecedented benzilic acid rearrangement involving migration of a carboxylate group to form 2-carboxy-l-lyxonolactone; the lactone is hydrolyzed by a member of the amidohydrolase superfamily to yield 2-carboxy-l-lyxonate. A member of the PdxA family of oxidative decarboxylases catalyzes a novel decarboxylation that uses NAD⁺ catalytically. The product, l-lyxonate, is catabolized to α-ketoglutarate by a previously characterized pathway. The pathway is found in hundreds of bacteria, including the pathogens <i>Pseudomonas aeruginosa</i> and <i>Acinetobacter baumannii</i>. << Less

  J Am Chem Soc 142:1657-1661(2020) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• Spontaneous hydrolysis and dehydration of dehydroascorbic acid in aqueous solution.

  Deutsch J.C.

  The interaction of water with dehydroascorbic acid was examined by incubating dehydroascorbic acid and ascorbic acid in 18O-labeled water for various amounts of time and then oxidizing the products with hydrogen peroxide or reducing the products with mercaptoethanol, with analysis by gas chromatog ... >> More

  The interaction of water with dehydroascorbic acid was examined by incubating dehydroascorbic acid and ascorbic acid in 18O-labeled water for various amounts of time and then oxidizing the products with hydrogen peroxide or reducing the products with mercaptoethanol, with analysis by gas chromatography mass spectrometry. Based on mass changes, dehydroascorbic acid readily exchanged three oxygen atoms with H218O. When mercaptoethanol was used to reduce dehydroascorbic acid (which had been incubated in H218O) to ascorbic acid, the newly formed ascorbic acid also contained three labeled oxygen atoms. However, ascorbic acid incubated in H218O for the same amount of time under identical conditions exchanged only two labeled oxygen atoms. Electron impact mass spectrometry of derivatized ascorbic acid created a decarboxylation product which had only two labeled oxygen atoms, regardless if 3-oxygen-labeled or 2-oxygen-labeled ascorbic acid was the parent compound, isolating the extra oxygen addition to carbon 1. These data suggest that dehydroascorbic acid spontaneously hydrolyzes and dehydrates in aqueous solution and that the hydrolytic-hydroxyl oxygen is accepted by carbon 1. Ascorbic acid, on the other hand, does not show this same tendency to hydrolyze. << Less

  Anal Biochem 260:223-229(1998) [PubMed] [EuropePMC]