Protein molecules have successfully been incorporated in bioelectronic molecular devices through the molecular wire or interface of conducting polymer. Such enzymes as glucose oxidase and fructose dehydrogenase were adsorbed on the platinum electrode surface, which was followed by the electropolymerization of pyrrole to deposit an ultimately thin layer of polypyrrole on the electrode surface. Alcohol dehydrogenase was immobilized in a polypyrrole membrane with NAD and Meldora’s blue in the similar manner on the electrode surface. The electron transfer from the electron transfer sites of these enzymes to the corresponding electrode has been promoted through the molecular wire. It has been demonstrated that the enzyme activity is modulated by changing the potential of the electrode with which the enzyme is connected through the molecular wire. On the basis of the electronic characteristics of these enzyme proteins the design principles of biomolecular electron devices have been proposed.