ChemRxiv
These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
1/1
0/0

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

preprint
submitted on 11.09.2019 and posted on 12.09.2019 by Tyler Stack, Katelyn Morrison, Thomas Dettmer, Brendan Wille, Chan Kim, Ryan Joyce, Madison Jermain, Yadanar Than Naing, Khadija Bhatti, Brian San Francisco, Michael S. Carter, John A. Gerlt

L-Ascorbate (vitamin C) is ubiquitous in both our diet and the environment. Ralstonia eutropha H16 (Cupriavidus necator ATCC 17699) uses L-ascorbate as sole carbon source but lacks the genes encoding the known catabolic pathways. RNAseq identified eight candidate catabolic genes. Sequence similarity networks and genome neighborhood networks guided predictions for function of the encoded proteins; 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 alpha-ketoglutarate by a previously characterized pathway.

Funding

P01GM118303

History

Email Address of Submitting Author

tstack@illinois.edu

Institution

University of Illinois – Urbana/Champaign

Country

United States of America

ORCID For Submitting Author

0000-0003-1422-784X

Declaration of Conflict of Interest

No conflict of interest

Exports

Read the published paper

in Journal of the American Chemical Society

Logo branding

Exports