Asymmetric bio-epoxidation catalyzed with the styrene monooxygenase from Pseudomonas sp. LQ26

Styrene monooxygenases (SMOs) can catalyze the asymmetric epoxidation of alkenes to obtain optically active epoxides. This account describes a series of work of our group on the isolation, application, and improvement of an SMO from Pseudomonas sp. LQ26. The strain was isolated from an active sludge sample based on indigo-forming capacity. Then the gene encoding SMO was expressed in Escherichia coli, and the whole cells were applied in biocatalytic reactions. The substrate spectrum of SMO was successfully expanded from conjugated styrene derivatives to non-conjugated alkenes, especially α-substituted secondary allylic alcohols, affording enantiopure epoxides. Most significantly, cascade reactions involving ketoreductase and SMO were designed, which resulted in glycidol derivatives or epoxy ketones with excellent enantio- and diastereo-selectivity using α,β-unsaturated ketones as the substrates. In addition, mutants of SMO with altered substrate preference and enhanced activity were constructed, which indicated great potential of SMO for further improvement.