Asymmetric Sulfoxidations Catalyzed by Bacterial Flavin-Containing Monooxygenases.

Flavin-containing monooxygenase from Methylophaga sp. ( m FMO) was previously discovered to be a valuable biocatalyst used to convert small amines, such as trimethylamine, and various indoles. As FMOs are also known to act on sulfides, we explored m FMO and some mutants thereof for their ability to convert prochiral aromatic sulfides. We included a newly identified thermostable FMO obtained from the bacterium Nitrincola lacisaponensis ( Ni FMO). The FMOs were found to be active with most tested sulfides, forming chiral sulfoxides with moderate-to-high enantioselectivity. Each enzyme variant exhibited a different enantioselective behavior. This shows that small changes in the substrate binding pocket of m FMO influence selectivity, representing a tunable biocatalyst for enantioselective sulfoxidations.