Enantioselective oxidation by a cyclohexanone monooxygenase from the xenobiotic-degrading Polaromonas sp. strain JS666

A cyclohexanone monooxygenase (CHMO) from the xenobiotic-degrading Polaromonas sp. strain JS666 was heterologously expressed in Escherichia coli, and its ability to catalyze enantio- and regiodivergent oxidations of prochiral and racemic ketones was investigated. The expression system was also used to evaluate this enzyme's potential role in the oxidation of cis-1,2-dichloroethene (cDCE), a groundwater pollutant for which strain JS666 is the only known assimilator. The substrate enantiopreference and -selectivity of the strain JS666 CHMO is similar to that of other CHMO-type enzymes; of note is this enzyme's excellent stereodiscrimination of 2-substituted cyclic ketones. The expression system exhibits no activity with ethene or cDCE as substrates under the tested conditions. Phylogenetic analysis shows that sequence variability among cyclohexanone monooxygenases could be a rich source of new enzyme activities and attributes.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A cyclohexanone monooxygenase from Polaromonas strain JS666 was cloned into Escherichia coli. ► Strain JS666 degrades cis-dichloroethene and many other xenobiotic compounds. ► This CHMO was highly enantioselective when oxidizing 2-substituted cyclohexanones. ► No activity on cis-dichloroethene was observed (contrary to a previous hypothesis).