An artificial electron donor supported catalytic cycle of Pseudomonas putida cytochrome P450_cam

Abstract

Putidaredoxin (PdX), the physiological effector of cytochrome P450_cam (P450_cam), serves to gate electron transfer into oxy-P450_cam during the catalytic cycle of the enzyme. Redox-linked structural changes in PdX are necessary for the effective P450_cam turnover reaction. PdX is believed to be difficult to be replaced by an artificial electron donor in the reaction pathway of P450_cam. We demonstrate that the catalytic cycle of wild-type P450_cam can be supported in the presence of an artificial reductant, potassium ferrocyanide. Upon rapid mixing of ferrocyanide ion with P450_cam, we observed an intermediate with spectral features characteristic of compound I. The rate constant for the formation of compound I in the presence of ferrocyanide supported reaction cycle was found to be comparable to the ones observed for H₂O₂ supported compound I formation in wild-type P450_cam, but was much lower than those observed for classical peroxidases. The results presented in this paper form the first kinetic analysis of this intermediate for an artificial electron-driven P450_cam catalytic pathway in solution.