ENZYME-CATALYZED DIRECT ELECTRON-TRANSFER - FUNDAMENTALS AND ANALYTICAL APPLICATIONS

This article overviews the fundamentals of the phenomenon of direct el ectron transfer in enzyme-catalyzed electrode reactions and the develo pment of electroanalytical applications of the bioelectrocatalytic sys tems. A brief description of the enzymes capable of catalyzing electro chemical reactions by means of direct electron transfer is given. The physico-chemical background of bioelectrocatalysis is discussed in ter ms of the different concepts underlying the mechanism of electron tran sfer. The concept of a ''molecular transducer'' is introduced to desig nate a complex, formed by the electrocatalytically active enzyme on th e electrode-electrolyte interface, which is directly responsible for t he transduction of the chemical signal to an electric one. The role of this ''molecular transducer'' in enzyme electrodes and immunoelectrod es is discussed. The analytical applications of bioelectrocatalysis ar e categorized as systems employing either amperometric or potentiometr ic detection. Discussion focuses on the advantages of systems based on enzyme-catalyzed direct electron transfer as opposed to other enzyme- catalyzed electroanalytical devices. In conclusion, the trends towards upcoming practical applications are suggested as well as some directi ons in fundamental studies of bioelectrocatalysis as a phenomenon.