Microbial Flavoprotein Monooxygenases as Mimics of Mammalian Flavin-Containing Monooxygenases for the Enantioselective Preparation of Drug Metabolites

Abstract

Mammalian flavin-containing monooxygenases, which are difficult to obtain and study, play a major role in detoxifying various xenobiotics. To provide alternative biocatalytic tools to generate flavin-containing monooxygenases (FMO)-derived drug metabolites, a collection of microbial flavoprotein monooxygenases, sequence-related to human FMOs, was tested for their ability to oxidize a set of xenobiotic compounds. For all tested xenobiotics [nicotine, lidocaine, 3-(methylthio)aniline, albendazole, and fenbendazole], one or more monooxygenases were identified capable of converting the target compound. Chiral liquid chromatography with tandem mass spectrometry analyses of the conversions of 3-(methylthio) aniline, albendazole, and fenbendazole revealed that the respective sulfoxides are formed in good to excellent enantiomeric excess (e.e.) by several of the tested monooxygenases. Intriguingly, depending on the chosen microbial monooxygenase, either the (R)-or (S)-sulfoxide was formed. For example, when using a monooxygenase from Rhodococcus jostii the (S)-sulfoxide of albendazole (ricobendazole) was obtained with a 95% e.e. whereas a fungal monooxygenase yielded the respective (R)-sulfoxide in 57% e.e. For nicotine and lidocaine, monooxygenases could be identified that convert the amines into their respective N-oxides. This study shows that recombinantly expressed microbial monooxygenases represent a valuable toolbox of mammalian FMO mimics that can be exploited for the production of FMO-associated xenobiotic metabolites.

Biotechnological Methods of Sulfoxidation: Yesterday, Today, Tomorrow

“…In turn, the R-sulfoxide of albendazole was obtained with an ee of 32%. It is worth noting that both CHMO Ac and BVMO Mt1 formed the same product as human FMO [73].…”

“…It was noted that Baeyer-Villiger Monooxygenases (BVMOs) from many microbes are sequentially associated with human FMO and exhibit similar effects; hence, they can be used as a tool to prepare metabolites in studies on the metabolism of xenobiotics [73].…”

“…In addition, the BVMOs used exhibited pronounced activity and excellent stereoselectivity in relation to prochiral prazole thioethers, such as omeprazoles, ilaprazoles, rabeprazoles, pantoprazoles, and lansoprazoles, which is a unique feature in this BVMO family [75]. It was noted that Baeyer-Villiger Monooxygenases (BVMOs) from many microbes are sequentially associated with human FMO and exhibit similar effects; hence, they can be used as a tool to prepare metabolites in studies on the metabolism of xenobiotics [73].…”

“…In turn, the R-sulfoxide o bendazole was obtained with an ee of 32%. It is worth noting that both CHMOAc and BVMOM rmed the same product as human FMO [73]. To solve the problems of stability of this enzyme, a number of CHMO mutants were generated rticularly noteworthy is the cyclohexanone monooxygenase mutant (CHMO-QM), whic ntained four distinct mutations C376L, M400I, T415C, and A463C.…”

“…Unfortunately, the formation of sulfone in an amount not exceeding 2% was also observed. This enzyme was also able to oxidize albendazole with a conversion of 55% and ee = 95% (S) [73].…”