Methanesulfonate monooxygenase (MSAMO) mediates the primary degradation of methanesulfonic acid (MSA) to produce formaldehyd and inorganic sulfite by initial hydroxylation of the carbon atom prior to spontaneous cleavage of the unstable hydroxymethanesulfonic acid. MSAMO has a restricted substrate range that includes only the short-chain aliphatic sulfonates (methane- to butanesulfonate) and excludes all larger molecules, such as arylsulfonates and aromatic sulfonates. All MSAMO components are required for enzyme activity. methanesulfonate + NADH + O2 = formaldehyde + H2O + NAD(+) + sulfite MSAMO is inhibited by metal chelators (such as bathophenanthroline, bathocuprione, neocuprione, alpha-alpha-dipyridil and sodium EDTA) and by sodium azide, sodium arsenate and potassium cyanide. Cell-free extracts of MSA-grown strain M2 have been used. Vmax of a cytoplasmic fraction has shown to be lower as was that of a reconstituted enzyme from partially purified fractions which was increased by addition of FAD and Fe(2+). The MSA monooxygenase system consists of 4 proteins: the 2 subunits of the hydroxylase component (MsmA and MsmB), a ferredoxin (MsmC) and a ferredoxin reductase (MsmD). The hydroxylase component consists of a 3 alpha (MsmA) and 3 beta (MsmB) subunits. The msmABCD operon is induced by methanesulfonic acid (MSA). Belongs to the bacterial ring-hydroxylating dioxygenase beta subunit family.