What can electrochemistry tell us about individual enzymes?

Abstract We provide here a critical analysis of electrochemistry's potential and limitations in investigating single-enzyme catalysis, highlighting papers of interest from the past 2–3 years with an emphasis on nano-impact electrochemistry (NIE) and electrochemical scanning tunneling microscopy. NIE can report single-enzyme activity; however, its future broad applicability for studying freely diffusing individual enzymes is questionable. Electrochemical scanning tunneling microscopy, an alternative to NIE, measures single enzyme's electronic conductivity when suspended between two electrodes. Recent discoveries indicate that enzyme conductance depends directly on biophysical parameters such as substrate binding, oxidation state of the catalytic center, and structural fluctuations. We conclude with a short perspective on additional electrochemical routes and combinations of existing techniques that may be useful for studying single-enzyme characteristics.