Monooxygenase that mediates oxidation of dimethyl sulfide, the first step in dimethyl sulfide degradation pathway. Has much lower activity with diethyl sulfide and other short-chain alkyl methyl sulfides. dimethyl sulfide + H(+) + NADH + O2 = formaldehyde + H2O + methanethiol + NAD(+) Inhibited by umbelliferone, 8-anilinonaphthalenesulfonate, a range of metal-chelating agents, and Hg(2+), Cd(2+) and Pb(2+) ions. Heterodimer of 2 subunits, DmoA and DmoB. DmoB has not been identified yet. Only a peptide from the protein encoded by a putative flavin reductase (AC E0XCR3) was obtained by mass spectrometry, which is insufficient for linking this gene to DmoB (PubMed:21216999). Belongs to the NtaA/SnaA/DszA monooxygenase family.