Characterization of choline trimethylamine-lyase expands the chemistry of glycyl radical enzymes

ACS Chem Biol. 2014 Jul 18;9(7):1408-13. doi: 10.1021/cb500113p. Epub 2014 Jun 2.


The recently identified glycyl radical enzyme (GRE) homologue choline trimethylamine-lyase (CutC) participates in the anaerobic conversion of choline to trimethylamine (TMA), a widely distributed microbial metabolic transformation that occurs in the human gut and is linked to disease. The proposed biochemical function of CutC, C-N bond cleavage, represents new reactivity for the GRE family. Here we describe the in vitro characterization of CutC and its activating protein CutD. We have observed CutD-mediated formation of a glycyl radical on CutC using EPR spectroscopy and have demonstrated that activated CutC processes choline to trimethylamine and acetaldehyde. Surveys of potential alternate CutC substrates uncovered a strict specificity for choline. Homology modeling and mutagenesis experiments revealed essential CutC active site residues. Overall, this work establishes that CutC is a GRE of unique function and a molecular marker for anaerobic choline metabolism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Choline / metabolism*
  • Cloning, Molecular
  • Desulfovibrio / genetics
  • Desulfovibrio / metabolism*
  • Electron Spin Resonance Spectroscopy
  • Enzyme Activation
  • Escherichia coli / genetics
  • Glycine / metabolism*
  • Humans
  • Lyases / metabolism*
  • Methylamines / metabolism*
  • Models, Molecular
  • Substrate Specificity


  • Bacterial Proteins
  • Methylamines
  • Lyases
  • trimethylamine
  • Choline
  • Glycine