Photochemical properties of a riboflavins/cytochrome P450 2B4 complex

The present study demonstrates the possible use of a non-covalent complex of riboflavins with cytochrome P450 2B4 (artificial flavocytochrome P450 2B4) for photo-induced intermolecular electron transfer between the isoalloxazine cycle of flavins and the ferric heme group of cytochrome P450 2B4. Riboflavin was used as a light-induced electron donor for the transfer of electrons to cytochrome P450. The quantitative measurement of the photocurrent, generated by photoreduction of non-covalent flavocytochrome P450 2B4, was carried out. In the presence of typical substrates for cytochrome P450 2B4 the decrease of cathodic photocurrent occurred, generated not only by riboflavin itself but also by a riboflavin/cytochrome P450 complex. It was demonstrated that flavocytochromes might serve as molecular amplifiers of a photocurrent, generated upon flavins' reduction. Introduction of flavin residues into the cytochrome P450 molecule transformed this haemoprotein into a photoreceptor and a photodiode and, in addition, into a photosensitive and photo-activated enzyme.