Direct electrochemistry of cytochrome P450 27B1 in surfactant films

We report the first direct electrochemistry of cytochrome P450 27B1 (CYP27B1) immobilized on an edge-plane pyrolytic graphite (EPG) electrode coated with a film of didodecyldimethylammonium bromide (DDAB). Cyclic voltammetry (CV) in a deoxygenated solution revealed excellent electrochemical reversibility with an average midpoint potential of -180 +/- 5 mV vs. Ag/AgCl and an apparent surface coverage of (7.0 +/- 2.5) x 10(13) molecules per cm(2). The rate of heterogeneous electron transfer between CYP27B1 and the EPG electrode was determined to be 3.5 +/- 0.6 s(-1). Upon addition of oxygen, a significant increase in cathodic current occurred, likely due to electrocatalytic reduction of dioxygen to peroxide and/or water by CYP27B1. Characterization of the electrochemical properties of CYP27B1 is an important first step toward developing a bioelectrochemical method for measuring vitamin D in serum. (C) 2009 Elsevier B.V. All rights reserved.