Recent Enzymatic Electrochemistry for Reductive Reactions

Abstract

Enzymatic electrochemistry is the coupling of oxidoreductase enzymes to electrodes, where electrons are transferred between the electrode and an enzyme's cofactor(s). In addition to enzymatic electrochemistry enabling mechanistic study [such as the determination of cofactor reduction potential(s)], enzymatic electrocatalysis also enables substrate reduction or oxidation by exploiting the catalytic properties of enzymes. This Minireview illustrates some recent examples, in which electrodes are coupled with enzymes that catalyze the reduction of substrates such as dinitrogen (N 2 ), carbon dioxide (CO 2 ) and protons (H + ), performed by metalloenzymes such as nitrogenases, formate dehydrogenases and hydrogenases. We review some strategies to achieve electron transfer (such as mediated and direct electron transfer), as well as some key results of recent studies.

Closing the Gap for Electronic Short‐Circuiting: Photosystem I Mixed Monolayers Enable Improved Anisotropic Electron Flow in Biophotovoltaic Devices

“…Thes elected redox polymers were chosen as they are capable of providing electrical wiring with enzymes performing reductive reactions of interest. [22] This has been shown recently for P-vio in combination with hydrogenases, [12,23] as well as for different cobaltocene-modified polymers in combination with hydrogenases, [7,24] formate dehydrogenase, [25] diaphorase for NADH regeneration purposes, [26] and nitrogenase. [27] Thep hotocurrent response was measured…”

Following Electroenzymatic Hydrogen Production by Rotating Ring–Disk Electrochemistry and Mass Spectrometry**

“…[6][7][8] While hydrogenases and nitrogenases accept reducing equivalents from small metalloproteins such as ferredoxins or flavodoxins in vivo, electrodes have been employed to drive the artificial reduction of H + and N 2 by these enzymes in vitro. [9][10][11][12][13] Such an approach is attractive not only for new biotechnologies but also for mechanistic interrogation of their complex catalytic mechanisms, whereby electron transfer to these gas-processing metalloenzymes can be controlled. Here, we demonstrate the use of rotating ring-disk electrochemistry (RRDE) as a technique to follow the production of H 2 from [FeFe]-hydrogenase from Clostridium pasteurianum (CpI) wired to a carbon electrode surface within a redox polymer (Figure 1).…”

Natural and Engineered Electron Transfer of Nitrogenase

“…The subsequent optimization of this MV electrochemical approach resulted in an observed rate constant for electron flux through nitrogenase when fixing N 2 approached the expected value of 13 s −1 (reported as 14 s −1 ), where rate-limiting electron transfer at 13 s −1 corresponds to an optimal TOF of 195 (accounting for re of H 2 ). Further, MV (and derivates) can also serve as an efficient electron donor to other (metallo)enzymes, such as formate dehydrogenases and hydrogenases, either for H 2 /formate (HCOO − ) oxidation or for H + /CO 2 reduction [152]. Of particular interest is the ability of MV to mediate electrons or enzymatic NADH formation [153,154].…”