ELECTRON-TRANSFER BETWEEN CELLOBIOSE DEHYDROGENASE AND GRAPHITE-ELECTRODES

Electron transfer between the enzyme cellobiose dehydrogenase (CDH) an d a flavin adenine dinucleotide (FAD) containing a catalytic active fr agment of CDH (FAD-fragment) and a graphite electrode, respectively, w as established. The current response in the presence of the enzyme sub strate for graphite electrodes with CDH or the FAD-fragment adsorbed o n the freshly polished graphite surface were compared with that of ele ctrodes where CDH or the FAD-fragment were crosslinked in a redox poly mer at the electrode surface. The initial slope, dj/d[S](S=0), where j is the current density and [S](S=0) the zero substrate concentration, was taken as a measure of the substrate response. For the electrodes with enzymes adsorbed directly on the surface, dj/d[S](S=0), was a fac tor of 3 lower than for electrodes prepared with the polymer mixture. The redox polymer based electrodes, with CDH and with FAD-fragment, bo th showed a high and close to equal substrate response. In contrast th e surface adsorbed CDH gave a much higher substrate response than the FAD-fragment.