Unspecific peroxygenases (UPOs, EC 1.11.2.1) are fungal biocatalysts that have attracted considerable interest for application in chemical syntheses due to their ability to selectively incorporate peroxide-oxygen into non-activated hydrocarbons. However, the number of available and characterized UPOs is limited, as it is difficult to produce these enzymes in homologous or hetero-logous expression systems. In the present study, we introduce a third approach for the expression of UPOs: cell-free protein synthesis using lysates from filamentous fungi. Biomass of Neurospora crassa and Aspergillus niger, respectively, was lysed by French press and tested for translational activity with a luciferase reporter enzyme. The upo1 gene from Cyclocybe (Agrocybe) aegerita (encoding the main peroxygenase, AaeUPO) was cell-free expressed with both lysates, reaching activities of up to 105 U L⁻¹ within 24 h (measured with veratryl alcohol as substrate). The cell-free expressed enzyme (cfAaeUPO) was successfully tested in a substrate screening that included prototypical UPO substrates, as well as several pharmaceuticals. The determined activities and catalytic performance were comparable to that of the wild-type enzyme (wtAaeUPO). The results presented here suggest that cell-free expression could become a valuable tool to gain easier access to the immense pool of putative UPO genes and to expand the spectrum of these sought-after biocatalysts.

Antithrombotic thienopyridines, such as clopidogrel and prasugrel, are prodrugs that undergo a metabolic two-step bioactivation for their pharmacological efficacy. In the first step, a thiolactone is formed, which is then converted by cytochrome P450-dependent oxidation via sulfenic acids to the active thiol metabolites. These metabolites are the active compounds that inhibit the platelet P2Y₁₂ receptor and thereby prevent atherothrombotic events. Thus far, described biocatalytic and chemical synthesis approaches to obtain active thienopyridine metabolites are rather complex and suffer from low yields. In the present study, several unspecific peroxygenases (UPOs, EC 1.11.2.1) known to efficiently mimic P450 reactions in vitro—but requiring only hydroperoxide as oxidant—were tested for biocatalytic one-pot syntheses. In the course of the reaction optimization, various parameters such as pH and reductant, as well as organic solvent and amount were varied. The best results for the conversion of 1 mM thienopyridine were achieved using 2 U mL⁻¹ of a UPO from agaric fungus Marasmius rotula (MroUPO) in a phosphate-buffered system (pH 7) containing 5 mM ascorbate, 2 mM h⁻¹ H₂O₂ and 20% acetone. The preparation of the active metabolite of clopidogrel was successful via a two-step oxidation with an overall yield of 25%. In the case of prasugrel, a cascade of porcine liver esterase (PLE) and MroUPO was applied, resulting in a yield of 44%. The two metabolites were isolated with high purity, and their structures were confirmed by MS and MS² spectrometry as well as NMR spectroscopy. The findings broaden the scope of UPO applications again and demonstrate that they can be effectively used for the selective synthesis of metabolites and late-state diversification of organic molecules, circumventing complex multistage chemical syntheses and providing sufficient material for structural elucidation, reference material, or cellular assays.

There is an enormous potential for cell-free protein synthesis (CFPS) systems based on filamentous fungi in view of their simple, fast and mostly inexpensive cultivation with high biomass space-time yields and in view of their catalytic capacity. In 12 of the 22 different filamentous fungi examined, in vitro translation of at least one of the two reporter proteins GFP and firefly luciferase was detected. The lysates showing translation of a reporter protein usually were able to synthesize a functional cell-free expressed unspecific peroxygenase (UPO) from the basidiomycete Cyclocybe (Agrocybe) aegerita. For the most promising candidate Neurospora crassa, the influence of different conditions of cultivation and lysate preparation on in vitro translation of the reporter proteins was investigated and optimized. In general, the greatest improvements in the translational activity were achieved by the choice of the growth medium, the addition of organic nitrogen being most beneficial. Optimizing the culture and preparation conditions of the N. crassa platform improved protein yield of the original lysate by a factor of 25 for firefly luciferase and 17 for GFP, respectively. In addition to the reporter proteins, the aforementioned UPO as well as a functional UPO from Aspergillus niger were cell-free expressed using the different lysates from N. crassa. CFPS with fungal lysates opens the door to expressing UPOs in high throughput and in parallel, for example to optimize synthesis conditions or adapt catalyst properties. The presented method proves the general potential of fungal lysates for application in cell-free syntheses.

Unspecific peroxygenases (UPO, EC 1.11.2.1) are a valuable tool for the biocatalytic synthesis of specialty chemicals such as pharmaceutical metabolites. However, the search for new UPOs that are recombinantly expressible can be tedious and dependent on expensive equipment, especially when a large number of clones has to be examined. In this study, we present a simple agar plate-based method for the screening of active, secreted UPOs heterologously expressed in Saccharomyces cerevisiae. This allows a real high-throughput of several thousand clones at once. The approach was successfully tested with a small gene library comprising putative UPO genes and resulted in the identification of two clones producing short UPOs from the filamentous fungi Dendrothele bispora (DbiUPO) and Aspergillus niger (AniUPO). Both UPOs were partly purified and characterized with respect to their catalytic properties. With differing efficiencies and product specificities, they catalyzed the formation of human drug metabolites, e.g., lipid mediators from polyunsaturated fatty acids and the active metabolite of the prodrug clopidogrel, respectively.

The metabolism of polyunsaturated fatty acids (PUFAs) is a broad research field, and the products identified so far offer potential medical and industrial applications. Epoxy fatty acids (EpFAs) act as lipid mediators that modulate renal function, angiogenesis, vascular dilatation and inflammation; moreover, they regulate monocyte aggregation and are involved in cardiovascular and metabolic diseases. On the other hand, EpFAs are precursors of environmentally friendly products for the plastics industry, in which the grade of epoxidation of the compounds gives the polymeric material different advantageous characteristics. The controlled chemical synthesis of poly epoxidized PUFAs is challenging as the reactions are non-selective. In contrast, the biosynthetic route based on cytochrome P450 monooxygenases and lipoxygenases is highly selective but ineffective due to the instability of the enzymes in cell-free systems. Fungal unspecific peroxygenases (UPOs, EC 1.11.2.1) with P450-like activity offer a suitable alternative for the selective synthesis of EpFAs from PUFAs. Here we demonstrate that a recombinant unspecific peroxygenase from Aspergillus niger (rAniUPO) is able to sequentially epoxidize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to 14,15-17,18 diepoxyeicosatrienoic acid (14,15-17,18 diEpETrE) and 16,17-19,20-diepoxydocosatetraenoic acid (16,17-19,20 diEpDTE), respectively, while arachidonic acid is transformed into 13-hydroxy-14,15-epoxyeicosatrienoic acid (14,15-hepoxilin B₃). Optimal production for these oxygenated derivatives (up to 15 mg) was achieved using 2 mM hydrogen peroxide as the co-substrate. The obtained molecules were identified using high-resolution mass spectrometry and their structure was verified by NMR. Our results demonstrate the suitability of UPOs for the synthesis of EpFAs that can be used in medical research and industrial applications.

N ‐Linked glycosylation can have a significant impact on the yield of heterologously expressed proteins secreted by Saccharomyces cerevisiae . The yeast is a widely used host for the expression of unspecific peroxygenases (UPOs), a subclass of peroxide‐dependent oxidoreductases with high potential for industrial biocatalytic applications. However, the effects of N ‐glycosylation on the expression of recombinant UPOs have not yet been investigated. Here, we studied respective protein modification on the expression of a UPO from Marasmius rotula , belonging to the protein subfamily of short peroxygenases, in S. cerevisiae . Two of the three N ‐glycosylation sites that are actually occupied in r Mro UPO were eliminated by substituting asparagine at positions N43 and N151 with serine. The single substitutions led to reduced amounts of secreted r Mro UPO, with N43S having the highest impact (almost four times lower protein amount compared to the native enzyme) and N151S having a moderate effect. In the next step, the glycosylation probability at position 43 was enhanced by replacing the serine in the corresponding sequon with threonine, which increased the expression of the r Mro UPO variant. The concentration of active UPO in the concentrated culture supernatant of the glycosylation‐optimised variant S45T was twice as high as that of the native r Mro UPO. The results suggest that N ‐linked glycosylation is an important factor for successful heterologous UPO expression in S. cerevisiae .