Physiology and Metabolism
Research Article
2 April 2024

Tetrahydrofolate levels influence 2-aminoacrylate stress in Salmonella enterica


In Salmonella enterica, the absence of the RidA deaminase results in the accumulation of the reactive enamine 2-aminoacrylate (2AA). The resulting 2AA stress impacts metabolism and prevents growth in some conditions by inactivating a specific target pyridoxal 5′-phosphate (PLP)-dependent enzyme(s). The detrimental effects of 2AA stress can be overcome by changing the sensitivity of a critical target enzyme or modifying flux in one or more nodes in the metabolic network. The catabolic L-alanine racemase DadX is a target of 2AA, which explains the inability of an alr ridA strain to use L-alanine as the sole nitrogen source. Spontaneous mutations that suppressed the growth defect of the alr ridA strain were identified as lesions in folE, which encodes GTP cyclohydrolase and catalyzes the first step of tetrahydrofolate (THF) synthesis. The data here show that THF limitation resulting from a folE lesion, or inhibition of dihydrofolate reductase (FolA) by trimethoprim, decreases the 2AA generated from endogenous serine. The data are consistent with an increased level of threonine, resulting from low folate levels, decreasing 2AA stress.


RidA is an enamine deaminase that has been characterized as preventing the 2-aminoacrylate (2AA) stress. In the absence of RidA, 2AA accumulates and damages various cellular enzymes. Much of the work describing the 2AA stress system has depended on the exogenous addition of serine to increase the production of the enamine stressor. The work herein focuses on understanding the effect of 2AA stress generated from endogenous serine pools. As such, this work describes the consequences of a subtle level of stress that nonetheless compromises growth in at least two conditions. Describing mechanisms that alter the physiological consequences of 2AA stress increases our understanding of endogenous metabolic stress and how the robustness of the metabolic network allows perturbations to be modulated.

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Published In

cover image Journal of Bacteriology
Journal of Bacteriology
Volume 206Number 418 April 2024
eLocator: e00042-24
Editor: George O'Toole, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
PubMed: 38563759


Received: 6 February 2024
Accepted: 12 March 2024
Published online: 2 April 2024


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  1. 2-aminoacrylate stress
  2. folate biosynthesis
  3. alanine racemase
  4. metabolic integration
  5. RidA

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All relevant data are included in the content of this article.



Department of Microbiology, University of Georgia, Athens, Georgia, USA
Author Contributions: Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft, and Writing – review and editing.
Department of Microbiology, University of Georgia, Athens, Georgia, USA
Author Contributions: Conceptualization, Formal analysis, Funding acquisition, Methodology, Resources, Supervision, and Writing – review and editing.


George O'Toole
Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA


The authors declare no conflict of interest.

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