Direct Electron Transfer Reaction of d-Gluconate 2-Dehydrogenase Adsorbed on Bare and Thiol-modified Gold Electrodes

Abstract

Direct electron transfer-type bioelectrocatalytic oxidation of d-gluconate was observed with d-gluconate 2-dehydrogenase (GADH, EC 1.1.99.3, from Gluconobacter frateurii) at bare and thiols-modified gold electrodes. Thiols used have different charges and various lengths of the alkyl chains. The catalytic current at every electrode arose at −0.05 V, which would correspond to the formal potential of the heme c site in GADH. The GADH-loading examined through quartz crystal microbalance measurements was practically independent of the surface properties. However, the current-potential curves were strongly affected by the electrode surface properties, and were interpreted in views of kinetics of enzymatic reaction and electrode reaction, and states of GADH on the electrode surface. The interfacial electron transfer rate constants of GADH depended on the alkane-chain lengths.