Electrochemical redox transformations of T1 and T2 copper sites in native Trametes hirsuta laccase at gold electrode

Mediator ess. electrochemically driven, redox transformations of TI (type 1) and T2 copper sites in Trametes hirsuta laccase were studied by cyclic voltarnmetry and spectroclectrochernical redox titrations using bare gold electrode. DET (direct electron transfer) between I he electrode and the enzyme was observed under anaerobic conditions. From analysis of experimental data it is concluded that the T2 copper site is in DET contact with gold. It was found that electron transfer between the gold surface and the TI copper site progresses through the T2 copper site. From EPR measurements and electrochemical data it is proposed that the redox potential of the T2 site for high-potential 'blue' laccase is equal to about 400 mV versus NHE (normal hydrogen electrode) at pH 6.5. The hypothesis that the redox potentials of the T2 copper sites in low- and high-potentiai laccases/oxiclases from totally different sources might be very similar, i.e. approx. 400 mV, is discussed.