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Clay-Bridged Electron Transfer between Cytochrome P450cam and Electrode

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Abstract

We demonstrate a very fast heterogeneous redox reaction of substrate-free cytochrome P450cam on a glassy carbon electrode modified with sodium montmorillonite. The linear relationship of the peak current in the cyclic voltammogram with the scan rate indicates a reversible one-electron transfer surface process. The electron transfer rate is in the range from 5 to 152 s−1 with scan rates from 0.4 to 12 V/s, respectively. These values are comparable to rates reported for the natural electron transfer from putidaredoxin to P450cam. The formal potential of adsorbed P450cam is −139 mV (vs NHE) and therefore positively shifted by 164 mV compared to the potential of substrate-free P450cam in solution. UV–VIS and FTIR spectra do not indicate an influence of the clay colloidal particles on the heme and the secondary structure of P450cam in solution. However, P450cam adsorbed on the surface of the clay-modified electrode may undergo partial dehydration resulting in the shift of the formal potential.

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    Abbreviations used: P450cam, cytochrome P450cam from Pseudomonas putida (CYP101); P420, denatured form of P450; Pdx, putidaredoxin; PdR, putidaredoxin reductase; FTIR, Fourier transform infrared spectroscopy; SMC, sodium montmorillonite colloid; GCE, glassy carbon electrode; Clay/GCE, clay-modified membrane on the electrode surface; PTFE, polytetrafluoroethylene; CV, cyclic voltammograms; P450/Clay/GCE, clay-modified electrode with adsorbed P450cam

    1

    Present address: Department of Chemical Engineering, Virginia Commonwealth University, Richmond, VA 23284-3028.

    2

    To whom correspondence may be addressed. (PD Dr. Jung) Fax: 0049-30-94063329, E-mail: [email protected]; or (Prof. Dr. Scheller) Fax: 0049-3371-681324, E-mail: [email protected].

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