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

Tyler M.M. Stack, Katelyn N. Morrison, Thomas M. Dettmer, Brendan Wille, Chan Kim, Ryan Joyce, Madison Jermain, Yadanar Than Naing, Khadija Bhatti, Brian San Francisco, Michael S. Carter, John A. Gerlt

Research output: Contribution to journalArticlepeer-review


l-Ascorbate (vitamin C) is ubiquitous in both our diet and the environment. Here we report that Ralstonia eutropha H16 (Cupriavidus necator 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 in vitro assays and in vivo growth phenotypes of gene deletion mutants. l-Ascorbate, a lactone, is oxidized and ring-opened by enzymes in the cytochrome b561 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 Pseudomonas aeruginosa and Acinetobacter baumannii.

Original languageEnglish (US)
Pages (from-to)1657-1661
Number of pages5
JournalJournal of the American Chemical Society
Issue number4
StatePublished - Jan 29 2020

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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