Expression of Pyridoxal 5'-Phosphate-Independent Racemases Can Reduce 2-Aminoacrylate Stress in Salmonella enterica

J Bacteriol. 2018 Apr 9;200(9):e00751-17. doi: 10.1128/JB.00751-17. Print 2018 May 1.


The RidA protein (PF01042) from Salmonella enterica is a deaminase that quenches 2-aminoacrylate (2AA) and other reactive metabolites. In the absence of RidA, 2AA accumulates, damages cellular enzymes, and compromises the metabolic network. In vitro, RidA homologs from all domains of life deaminate 2AA, and RidA proteins from plants, bacteria, yeast, and humans complement the mutant phenotype of a ridA mutant strain of S. enterica In the present study, a methanogenic archaeon, Methanococcus maripaludis S2, was used to probe alternative mechanisms to restore metabolic balance. M. maripaludis MMP0739, which is annotated as an aspartate/glutamate racemase, complemented a ridA mutant strain and reduced the intracellular 2AA burden. The aspartate/glutamate racemase YgeA from Escherichia coli or S. enterica, when provided in trans, similarly restored wild-type growth to a ridA mutant. These results uncovered a new mechanism to ameliorate metabolic stress, and they suggest that direct quenching by RidA is not the only strategy to quench 2AA.IMPORTANCE 2-Aminoacrylate is an endogenously generated reactive metabolite that can damage cellular enzymes if not directly quenched by the conserved deaminase RidA. This study used an archaeon to identify a RidA-independent mechanism to prevent metabolic stress caused by 2AA. The data suggest that a gene product annotated as an aspartate/glutamate racemase (MMP0739) produces a metabolite that can quench 2AA, expanding our understanding of strategies available to quench reactive metabolites.

Keywords: 2-aminoacrylate; archaeal metabolism; aspartate/glutamate racemase; endogenous stress; heterologous gene expression.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acrylates / chemistry*
  • Amino Acid Isomerases / genetics
  • Amino Acid Isomerases / metabolism
  • Aminohydrolases / genetics
  • Aminohydrolases / metabolism
  • Aspartic Acid / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression Regulation, Bacterial
  • Methanococcus / genetics
  • Methanococcus / metabolism
  • Pyridoxal Phosphate / metabolism*
  • Racemases and Epimerases / genetics
  • Racemases and Epimerases / metabolism*
  • Salmonella enterica / enzymology
  • Salmonella enterica / genetics*


  • Acrylates
  • Bacterial Proteins
  • Aspartic Acid
  • Pyridoxal Phosphate
  • Aminohydrolases
  • Racemases and Epimerases
  • Amino Acid Isomerases
  • glutamate racemase