Glutathione S‑Transferase Mediated Epoxide Conversion: Functional and Structural Properties of an Enantioselective Catalyst

Styrene is a naturally occurring but mainly anthropogenically produced aromatic compound. It is degraded via different routes in nature but often activated to styrene oxide, predominantly to its (S)-enantiomer. Hence, downstream enzymes should have regio- and enantio-preference. We have now demonstrated the enantioselectivity for a previously unknown class of bacterial glutathione S-transferases (GST) using both structural and kinetic approaches. Four actinobacterial GSTs were tested for their activity and selectivity. The most promising enzyme, GrStyI from Gordonia rubripertincta CWB2, was further investigated regarding its enantioselectivity and unique structure. GrStyI occurs as a homodimer and accepts (S)-styrene oxide (76 ± 3 μmol min–1 mg–1). It appears to be promiscuous in terms of structurally related epoxides and efficient for kinetic racemic resolution, providing a means for simple access toward (R)-epoxides, as we show in this study. We propose the presence of enantioselective GSTs in actinobacteria, forming the class of Actino-like GSTs.