Peroxide-driven catalysis of the heme domain of A. radioresistens cytochrome P450 116B5 for sustainable aromatic rings oxidation and drug metabolites production.

The heme domain of cytochrome P450 116B5 from Acinetobacter radioresistens (P450 116B5hd), a self-sufficient class VII P450, was functionally expressed in Escherichia coli, purified and characterised in active form. Its unusually high reduction potential (-144 ± 42 mV) and stability in the presence of hydrogen peroxide make this enzyme a good candidate for driving catalysis with the so-called peroxide shunt, avoiding the need for a reductase and the expensive cofactor NAD(P)H. The enzyme is able to carry out the peroxide-driven hydroxylation of aromatic compounds such as p-nitrophenol (KM = 128.85 ± 29.51 μM and kcat = 2.65 ± 0.14 min-1), 10-acetyl-3,7-dihydroxyphenoxazine (KM = 6.01 ± 0.32 μM and kcat = 0.33 ± 0.03 min-1), and 3,5,3',5'tetramethylbenzidine (TMB). Moreover, it catalyses different reactions on well-known drugs such as hydroxylation of diclofenac (KM = 49.60 ± 6.30 μM and kcat = 0.06 ± 0.01 min-1) and N-desmethylation of tamoxifen (KM = 57.20 ± 7.90 μM and kcat = 0.79 ± 0.04 min-1). The data demonstrate that P450 116B5hd is an efficient biocatalyst for sustainable applications in bioremediation and human drug metabolite production.