OBSERVATION OF DIRECT ELECTRON-TRANSFER FROM THE ACTIVE-CENTER OF GLUCOSE-OXIDASE TO A GRAPHITE ELECTRODE ACHIEVED THROUGH THE USE OF MILD IMMOBILIZATION

An immobilization method based on the use of aminophenylboronic acid enhanced the rate of electron transfer between glucose oxidase and a graphite electrode. Under anaerobic conditions, a group of 21 electrodes responded to a 10 mM change in glucose concentration with an average change of current of 0.5 +/- 0.1 mu A. Experimental evidence ruled out the possibility of (natural or artificial) mediated electron transfer or a mechanism based on orientation of the enzyme. A mechanism for electron transfer promotion based on the prevention by aminophenylboronic acid of the removal of the FAD from enzymes well situated and/or oriented to transfer electrons directly is postulated. To support this mechanism, experimental evidence was found confirming the removal of FAD from the enzyme by the graphite electrode and a protective role against it of aminophenylboronic acid.