Electrochemical Observation of Redox Centers of Bilirubin Oxidase and their Participation in Electrocatalytic Reduction of Oxygen

摘要: The understanding of the mechanism oxygen electroreduction by blue multicopper oxidases is a prerequisite for application these enzymes in bioanalysis and biofuel cells. Mediated direct electron transfer (MET DET) reactions between Trachyderma tsunodae Myrothecium verrucaria bilirubin (BOD) carbon or gold electrodes have been studied under both anaerobic aerobic conditions using cyclic voltammetry, chronoamperometry, potentiometry, spectroelectrochemsitry. Well-pronounced DET-based bioelectroreduction O2 starting at very positive potential (>700 mV vs. NHE) with half wave equal to redox T1 site was shown on BOD-modified graphite (BOD-GE). In spite quite low values standard rate constants (ET) calculated transformation primary acceptors, enzyme (0.4 s), maximum biocatalytic current density relatively high, viz. 0.5 mAcm. contrast BOD-GE, only minor bioelectrocatalysis obtained case immobilized enzymes. This because main fraction BODs oriented electrode surface T2/T3 cluster fast ET BOD progresses, most probably, through T2 copper site, resulting slow catalytically irrelevant complete reduction needed H2O. relevant potentials centers enzymes, probably one states cluster, were measured be ca. 690 390 mV, respectively. indicate that an uphill process might ratedetermining step certain conditions. addition, corresponding resting form estimated 360 NHE. Bioelectrochemical perspectives will presented.