Metabolism of methanesulfonic acid involves a multicomponent monooxygenase enzyme

A novel methylotroph, strain M2, capable of utilizing methanesulfonic acid (MSA) as a sole source of carbon and energy was the subject of these investigations. The initial step in the biodegradative pathway of MSA in strain M2 involved an inducible NADH-specific monooxygenase enzyme (MSAMO). Partial purification of MSAMO from cell-free extracts by ion-exchange chromatography led to the loss of MSAMO activity. Activity was restored by the mixing of three distinct protein fractions designated A, B and C. The reconstituted enzyme had a narrow substrate specificity relative to crude cell-free extracts. Addition of FAD and ferrous ions to the reconstituted enzyme complex resulted in a fivefold increase in enzyme activity, suggesting the loss of FAD and ferrous ion from the multicomponent enzyme on purification. Analysis of mutants of strain M2 defective in the metabolism of C1 compounds indicated that methanol was not an intermediate in the degradative pathway of MSA and also confirmed the involvement of a multicomponent enzyme in the degradation of MSA by methylotroph strain M2.