In E. coli, TMAO reductase is encoded by the torCAD operon. The torC gene encodes a pentahemic c-type cytochrome (TorC). TorC is likely to transfer electrons directly to the periplasmic TorA terminal enzyme encoded by the torA gene. The anaerobic expression of the torCAD operon is strictly controlled by the presence of TMAO or related compounds.
There are several different metabolic pathways that involve TMAO and TMA. The reduction of TMAO to TMA, catalyzed by TMAO reductase, as part of the electron transport chain follows the following reaction:
NADH + H + trimethylamine N-oxide  NAD + trimethylamine + HO
However, both the R. denitrificans and E. coli enzymes can accept electrons from cytochromes:
:trimethylamine + 2 (ferricytochrome c)-subunit + HO → trimethylamine N-oxide + 2 (ferrocytochrome c)-subunit + 2 H
Other reactions involving TMAO and TMA include:
* The oxidation of TMA to TMAO, which occurs in some methylotrophs as an initial step in utilizing TMA as a source of carbon
* The demethylation of TMAO to dimethylamine and formaldehyde by methylotrophs
* The oxidative demethylation of TMA to dimethylamine and formaldehyde by methylotrophs
* The production of methane from TMA and other methylamines by some methanogens