The self-sufficient P450 RhF expressed in a whole cell system selectively catalyses the 5-hydroxylation of diclofenac.

P450 monooxygenases are able to catalyze the highly regio- and stereoselective oxidations of many organic molecules. However, the scale-up of such bio-oxidations remains challenging due to the often-low activity, level of expression and stability of P450 biocatalysts. Despite these challenges they are increasingly desirable as recombinant biocatalysts, particularly for the production of drug metabolites. Diclofenac is a widely used anti-inflammatory drug that is persistent in the environment along with the 4'- and 5-hydroxy metabolites. Here we have used the self-sufficient P450 RhF (CYP116B2) from Rhodococcus sp. in a whole cell system to reproducibly catalyze the highly regioselective oxidation of diclofenac to 5-hydroxydiclofenac. The product is a human metabolite and as such is an important standard for environmental and toxicological analysis. Furthermore, access to significant quantities of 5-hydroxydiclofenac has allowed us to demonstrate further oxidative degradation to the toxic quinoneimine product. Our studies demonstrate the potential for gram-scale production of human drug metabolites through recombinant whole cell biocatalysis.