Characterization of choline trimethylamine-lyase expands the chemistry of glycyl radical enzymes.
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.
Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
Smaranda
S
Craciun
Jonathan A
JA
Marks
Emily P
EP
Balskus
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D003001:Cloning, Molecular; D003901:Desulfovibrio / Q000235:genetics / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics; D005998:Glycine / Q000378:metabolism*; D006801:Humans; D008190:Lyases / Q000378:metabolism*; D008744:Methylamines / Q000378:metabolism*; D008958:Models, Molecular; D013379:Substrate Specificity
D001426:Bacterial Proteins; D008744:Methylamines; D008190:Lyases; C023336:trimethylamine; D002794:Choline; D005998:Glycine