INTERPRETING THE CATALYTIC VOLTAMMETRY OF ELECTROACTIVE ENZYMES ADSORBED ON ELECTRODES

Steady-state electrocatalytic waveforms displayed by redox enzymes ads orbed on electrodes are analyzed to reveal and quantify important mech anistic characteristics of the active sites involved in catalysis and to elucidate the contributions of different factors in determining the overall electron-transport rates. The shape, height, steepness, and p otential of the voltammetric waves are functions of mass transport, in terfacial electron-transfer rates, and the intrinsic kinetic and therm odynamic properties of the enzyme. A model is constructed first for th e most simple realistic case, an enzyme containing a single two-electr on active site, and then this is extended to include additional electr on-transfer centers that serve as intramolecular relays. Equations are derived that predict the steady-state behavior expected for different conditions, and the models are used to assess recent experimental res ults. An alternative perspective on enzyme catalytic electron-transpor t is thus presented, in which kinetics and energetics are viewed and a nalyzed in the potential domain.