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

Abstract

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.

Two-Component FAD-Dependent Monooxygenases: Current Knowledge and Biotechnological Opportunities

“…have been characterized in detail [ 121 , 129 , 130 , 131 , 132 ]. StyAs showed the ability to convert a variety of styrene derivatives as well as aryl alkyl sulfides in a regio- and enantioselective manner [ 43 , 121 , 129 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 ].…”

Production of Enantiopure Chiral Epoxides with E. coli Expressing Styrene Monooxygenase

“…Initially, SMOs were considered as enzymes with a narrow substrate spectrum, especially those originating from Pseudomonas and Rhodococcus species. However, recent studies described novel SMOs from various bacteria or metagenome, which provided novel insights into the catalytic mechanism of styrene epoxidation and, thereby, enabled the generation of SMOs with improved biocatalytic activities and a broader substrate spectrum [ 4 , 6 , 14 , 30 ]. So far, all studies have confirmed that few structural characteristics of the substrate significantly impact the biocatalysis: acyclic double bonds are preferred; an electron-withdrawing group conjugated to a double bond, α-/β-substitution of styrene/styrene derivatives, as well as 2-substitution of an aromatic ring decrease activity [ 5 , 6 , 12 , 13 , 31 ].…”

“…Initially, wild-type SMOs of Pseudomonas were widely employed for biotransformation of styrene, but, to date, many other bacterial species that share styrene degradation pathways have been described [ 1 ]. Such discoveries, together with the expansion of recombinant technologies, metagenomics, and protein engineering, have led to the generation of SMOs with higher stability, selectivity, and activity towards a broad substrate spectrum, usually expressed as recombinant enzymes in Escherichia coli [ 2 , 4 , 5 , 6 , 7 ]. Significant progress was achieved by Panke et al in previous studies [ 8 , 9 , 10 , 11 ].…”