Cytochrome P450 5208A3 is a promiscuous xenobiotic biotransforming enzyme in Cunninghamella elegans

Cunninghamella elegans is a long-established microbial model of mammalian drug and xenobiotic metabolism enabled by the actions of cytochrome P450 enzymes that are poorly characterised. In this paper we describe the identification of a new cytochrome P450 (CYP) monooxygenase in the fungus that catalyses the biotransformation of a range of structurally distinct xenobiotic substrates. The fungal enzyme was heterologously expressed in the yeast Pichia pastoris X-33 alone and in combination with previously identified C. elegans CYP reductases (CPRs A, B and C). Enzyme activity was assessed against a panel of drugs (flurbiprofen, diclofenac and ibuprofen), pesticides (transfluthrin, β-cyfluthrin and λ-cyhalothrin) and a perfluoroalkyl substance (6:2 fluorotelomer alcohol) that were incubated with whole yeast cells expressing CYP5208A3. The biotransformation products were determined by gas chromatography-mass spectrometry (GC-MS) revealing the same metabolites that had been previously observed in the fungus. Co-expression of the CPRs improved metabolite production and the degree of improvement depended on the substrate and the CYP/CPR combination. Optimal pyrethroid biotransformation was achieved with CYP/CPR_C, whereas the best combination for non-steroidal anti-inflammatory drug hydroxylation was CYP/CPR_A; fluorotelomer alcohol oxidation was only observed with CYP/CPR_B. The change in substrate specificity observed with CYP5208A3 in combination with the different CPRs might help explain how C. elegans can biotransform such a broad spectrum of xenobiotics.