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. By TMAO and DMSO. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has been experimentally proven. Although torA is induced by both TMAO and DMSO, only TMAO is used as a natural substrate. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.