Direct Bioelectrocatalysis Research Articles

Enzyme-catalysed electrochemical oxidation of d-gluconate at electrodes coated with d-gluconate dehydrogenase, a membrane-bound flavohemoprotein

d-gluconate dehydrogenase was dip coated onto ordinary electrodes of carbon paste, glassy carbon, pyrolytic graphite, gold, silver, platinum or mercury. Surface redox waves clearly attributable to the reaction of the adsorbed enzyme were not observed. Nevertheless, all the electrodes with the adsorbed enzyme produced anodic currents for the electrocatalytic oxidation of d-gluconate. Neither electron transfer mediators nor promoters were necessary. The adsorbed enzyme was stable enough at pH 5.0 and at 5°C to allow the quantitative study of electrocatalysis. The current-potential curve for the catalytic oxidation reaction has an unusual shape, starting at −0.14 V with a hump at about 0.02–0.05 V vs. Ag/AgCl. A steady state current was obtained at fixed electrode potentials and the current increased with increasing concentrations of the substrate to approach saturation. The results could be described by an equation of direct bioelectrocatalysis at an electrode coated with an enzyme. A probable candidate for the redox site of the enzyme that donates electrons to the electrode was heme c.

Direct Bioelectrocatalysis at Metal and Carbon Electrodes Modified with Adsorbed d-Gluconate Dehydrogenase or Adsorbed Alcohol Dehydrogenase from Bacterial Membranes

Abstract d-Gluconate dehydrogenase, a flavohemoprotein, and alcohol dehydrogenase, a quinohemoprotein, are adsorbed strongly on carbon and metal electrodes. All the electrodes with the adsorbed enzymes produce anodic currents due to the electro-enzymatic oxidation of the substrates, where the adsorbed enzymes donate electrons directly to the electrodes; neither mediators nor promoters are necessary.

Amperometric fructose sensor based on direct bioelectrocatalysis

Fructose dehydrogenase (EC 1.1.99.11) from bacterial membranes was immobilized on a carbon paste electrode by covering the enzyme layer with a dialysis membrane. The fructose dehydrogenase-modified carbon paste electrode showed a current response to d-fructose without the addition of any external electron transfer mediators. The current response was independent of the oxygen concentration in the solution. Steady-state currents were obtained when measured at fixed electrode potentials. The dependence of the steady-state current on the potential, the pH of the solution and the temperature was studied. On the basis of this investigation, it was shown that the fructose dehydrogenase-modified carbon paste electrode could be used as an unmediated amperometric fructose sensor. d-Fructose in fruits was measured using the present electrode. A method of eliminating the effect of l-ascorbic acid is also described.

Direct Bioelectrocatalysis at Electrodes Modified with d--Gluconate Dehydrogenase

Direct Bioelectrocatalysis at Electrodes Modified with <scp>d-</scp>-Gluconate Dehydrogenase

Direct bioelectrocatalysis at electrodes modified with D-gluconate dehydrogenase.

d-Gluconate dehydrogenase isolated from Pseudomonas fluorescens was immobilized on the surfaces of carbon and gold electrodes by irreversible adsorption. The electrodes with the adsorbed enzyme produced anodic currents in solutions containing d-gluconate. The currents were attributable to the electro-enzymic oxidation (direct bioelectrocatalytic oxidation) of d-gluconate; the electrochemical system required no external redox molecules serving as mediators of electron transfer between the electrode and the adsorbed enzyme. A model of the direct bioelectrocatalysis at the enzyme-modified electrodes is presented.