Reduces trimethylamine-N-oxide (TMAO) into trimethylamine; an anaerobic reaction coupled to energy-yielding reactions. 2 Fe(III)-[cytochrome c] + H2O + trimethylamine = 2 Fe(II)-[cytochrome c] + 3 H(+) + trimethylamine N-oxide Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Interacts with the N-terminal domain of TorC. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.