Cloning, expression, and characterization of Baeyer-Villiger monooxygenases from eukaryotic Exophiala jeanselmei strain KUFI-6N.

The fungus Exophiala jeanselmei strain KUFI-6N produces a unique cycloalkanone monooxygenase (ExCAMO) that displays an uncommon substrate spectrum of Baeyer-Villiger oxidation of 4-10-membered ring ketones. In this study, we aimed to identify and sequence the gene encoding ExCAMO from KUFI-6N and overexpress the gene in Escherichia coli. We found that the primary structure of ExCAMO is most closely related to the cycloalkanone monooxygenase from Cylindrocarpon radicicola ATCC 11011, with 54.2% amino acid identity. ExCAMO was functionally expressed in E. coli and its substrate spectrum and kinetic parameters were investigated. Substrate profiling indicated that ExCAMO is unusual among known Baeyer-Villiger monooxygenases owing to its ability to accept a variety of substrates, including C4-C12 membered ring ketones. ExCAMO has high affinity and catalytic efficiency toward cycloalkanones, the highest being toward cyclohexanone. Five other genes encoding Baeyer-Villiger monooxygenases were also cloned and expressed in E. coli.