Comparison of bioelectrocatalysis at Trichaptum abietinum and Trametes hirsuta laccase modified electrodes

Bioelectrocatalytic reduction of oxygen to water at electrodes modified with gold nanoparticles and a new laccase from Trichaptum abietinum (TaLc) was studied. The bioelectrocatalytic current was found to be much higher at TaLc modified electrodes than at similarly prepared electrodes modified with a broadly used laccase from Trametes hirsuta (ThLc). To explain this difference the bioelectrocatalysis was described in terms of kinetic rate constants based on simultaneous cyclic voltammetry and quartz crystal microbalance measurements. From analysis of the rate constants both laccases appeared to possess similar rates (k₀) of direct electron transfer. However, the enzyme turnover (k_cat) was about three-fold higher for gold nanoparticle bound TaLc than for ThLc, calculated using surface concentration of enzyme established by QCM-D. Near reversible potential-induced reorientation of adsorbed proteins was observed by surface enhanced Raman spectroscopy.