Cytochrome P450-mediated metabolic engineering: current progress and future challenges

•P450s catalyze critical steps in all branches of plant specialized metabolism.•P450-driven engineering has been successful in both microorganisms and plants.•It is not a straightforward process and requires multistep optimizations.•Optimizations of the electron and metabolic fluxes are critical aspects. Cytochromes P450 catalyze a broad range of regiospecific, stereospecific and irreversible steps in the biosynthetic routes of plant natural metabolites with important applications in pharmaceutical, cosmetic, fragrance and flavour, or polymer industries. They are consequently essential drivers for the engineered bioproduction of such compounds. Two ground-breaking developments of commercial products driven by the engineering of P450s are the antimalarial drug precursor artemisinic acid and blue roses or carnations. Tedious optimizations were required to generate marketable products. Hurdles encountered in P450 engineering and their potential solutions are summarized here. Together with recent technical developments and novel approaches to metabolic engineering, the lessons from this pioneering work should considerably boost exploitation of the amazing P450 toolkit emerging from accelerated sequencing of plant genomes.