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J Biotechnol. 2019 Jan 28. pii: S0168-1656(19)30017-3. doi: 10.1016/j.jbiotec.2019.01.011. [Epub ahead of print]

Type II flavoprotein monooxygenase PsFMO_A from the bacterium Pimelobacter sp. Bb-B catalyzes enantioselective Baeyer-Villiger oxidations with a relaxed cofactor specificity.

Author information

1
Chair of Organic Chemistry I, Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany.
2
Chair of Algae Biotechnology & Bioenergy, Faculty of Biology, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany.
3
Chair of Algae Biotechnology & Bioenergy, Faculty of Biology, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany. Electronic address: olaf.kruse@uni-bielefeld.de.
4
Chair of Organic Chemistry I, Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany. Electronic address: harald.groeger@uni-bielefeld.de.

Abstract

Microbial consortia, which degrade branched, long-chain hydrocarbons, can be regarded as a promising source of novel enzymes for the stereo- and regio-selective oxyfunctionalization of hydrocarbons. The hydrocarbon-degrading bacterium Pimelobacter sp. Bb-B was isolated from the consortium associated with the colonial hydrocarbon-excreting microalga Botryococcus braunii. Three new type II flavoprotein monooxygenases (type II FMOs) from this bacterium have been made available in recombinant form through cloning and overexpression in an E. coli host organism. These enzymes (PsFMO_A-C) were characterized in terms of their capability of catalyzing Baeyer-Villiger oxidations with distinct substrates. The highest activity was detected when utilizing camphor and bicyclo[3.2.0]hept-2-en-6-one as substrate in combination with PsFMO_A as the most promising enzyme. Furthermore, synthetic biotransformations with 5 mM of the substrate bicyclo[3.2.0]hept-2-en-6-one, formate and formate dehydrogenase for in situ-cofactor recycling were conducted with this enzyme, leading to a substrate consumption of 85% after 66 h and excellent enantioselectivity of 99% ee for the (1R,5S)-enantiomer. Additionally, an alternative in situ-cofactor recycling based on the use of microalgae for in situ-production of formate from carbon dioxide, water and light together with a formate dehydrogenase was combined successfully with the enzyme PsFMO_A, leading to a substrate consumption of 94% and an enantioselectivity of >99% ee for the so-called "normal lactone"-enantiomer with the absolute configuration 1R,5S.

KEYWORDS:

Asymmetric synthesis; Botryococcus braunii; Lactones; Pimelobacter sp.; Type II flavoprotein monooxygenases Baeyer-Villiger oxidation

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