Abbreviations: ALA, aminolevulinic acid; BM3, cytochrome P450 from Bacillus megaterium; cdw, cell dry weight; cww, cell wet weight; HPLC, high--performance liquid chromatography; IMAC, immobilised metal affinity chromatography; IPTG, isopropyl β--D--1--thiogalactopyranoside; IR, infrared; MS, mass spectrometry; NADPH, nicotinamide adenine dinucleotide phosphate; NMR, nuclear magnetic resonance; NSAID, non--steroidal anti--inflammatory drug; P450, cytochrome P450 monooxygenase; RhF, cytochrome P450 from Rhodococcus sp. strain NCIMB 9784.
4Abstract P450 monooxygenases are able to catalyse 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 catalyse 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.
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