Asymmetric Sulfoxidations Catalyzed by Bacterial Flavin-Containing Monooxygenases.

Flavin-containing monooxygenase from sp. (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 FMO and some mutants thereof for their ability to convert prochiral aromatic sulfides. We included a newly identified thermostable FMO obtained from the bacterium (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 FMO influence selectivity, representing a tunable biocatalyst for enantioselective sulfoxidations.