Epoxidation, hydroxylation and aromatization is catalyzed by a peroxygenase from Solanum lycopersicum

Plant peroxygenase (PXG) oxidizes unsaturated fatty acids by transferring an oxygen atom of a hydroperoxide to the double bond, thereby providing epoxides. In this work we investigated the potential of a PXG from tomato (Solanum lycopersicum, SlPXG) to catalyze the oxidation of a variety of natural products. A SlPXG gene was cloned from tomato, heterologously expressed in yeast and the membrane bound recombinant SlPXG protein was used as enzyme source. Unsaturated fatty acids, fatty acid derivatives, and terpenes were epoxidized by SlPXG in the presence of various hydroperoxides exclusively at their cis-double bonds. Terpenes with p-menthene skeleton were transformed in different ways depending on their molecular structures. R-(+)- and S-(−)-limonene were converted to R-(+)-limonene-trans-1,2-epoxide (97%) and cis-S-(−)-limonene-1,2-epoxide (88%), respectively whereas α-terpinene was hydroxylated to cis-1,4-dihydroxy-p-menth-2-ene and γ-terpinene was aromatized to p-cymene. In the last reaction the hydroperoxide served as hydrogen acceptor rather than an oxygen donor. PXG appears to be a versatile biocatalyst able to perform different kinds of oxidation reactions. As no cofactors like NAD(P)H are required and H2O2 is an environmentally friendly oxidant, PXG enables new applications for the synthesis of fine chemicals from renewable resources.