Direct electrical communication between chemically modified enzymes and metal electrodes. II. Methods for bonding electron- transfer relays to glucose oxidase and D-Amino-Acid oxidase.

Foavoenzymes, such as glucose oxidase and D-amino-acid oxidase do not directly transfer electrons to conventional electrodes, because the distance between their redox centers and the electrodes' surface exceeds, even on closest approach, the distance across which electrons are transferred at sufficient rates. After chemical bonding of an average of one electron-transfer relay to each 12,000-75,000 daltons of enzyme, the substrate-reduced enzymes are, however, directly oxidized at gold, platinum or carbon electrodes. Fast redox-couples, having redox potentials 0.07-055V positive of the redox-potentials of the apoenzyme- bound FAD/FADH sub 2 coenzymes (Edegrees = 0.05V SHE), are effective relays when covalently or coordinatively bound to the enzyme's proteins.