Broadening the Biocatalytic Toolbox - Screening and Expression of New Unspecific Peroxygenases

Unspecific peroxygenases (UPOs) catalyze the selective transfer of single oxygen atoms from peroxides to a broad range of substrates such as un-activated hydrocarbons. Since specific oxyfunctionalizations are among the most-desired reactions in synthetic chemistry, UPOs are of high industrial interest. To broaden the number of available enzymes, computational and experimental methods were combined in this study. After a comparative alignment and homology modelling, the enzymes were expressed directly in P. pastoris. Out of ten initially selected sequences, three enzymes (one from Aspergillus niger and two from Candolleomyces aberdarensis) were actively expressed. Cultivation of respective expression clones in a bioreactor led to production titers of up to 300 mg L-1. Enzymes were purified to near homogeneity and characterized regarding their specific activities and pH-optima for typical UPO substrates. This work demonstrated that directed evolution is not necessarily required to produce UPOs in P. pastoris at respective titers. The heterologous producibility of these three UPOs will expand the toolbox of available enzymes and help to advance their synthetic application.