This communication reports the first electrochemical study of the human P450 2E1 either absorbed or covalently linked to different electrode surfaces. Glassy-carbon and gold electrodes gave reversible electrochemical signals of an active P450 2E1. Molecular modeling of the enzyme helped to rationalize the results. A monolayer coverage was obtained on gold modified with cystamine/maleimide that covalently linked surface accessible cysteines of P450 2E1. The midpoint potential measured for the oriented P450 2E1 was -177 +/- 5 mV comparable to that of the FeIII/FeII of other P450 enzymes. The observed electron-transfer rate for this electrode was 10 s-1. The turnover of the active enzyme was measured with the P450 2E1 specific substrate p-nitrophenol, resulting in a KM of 130 +/- 3 muM and the formation of 2.2 muM of the p-nitrocatechol product upon application of a -300 mV bias.