scholarly journals Direct enzymatic bioelectrocatalysis: differentiating between myth and reality

2017 ◽  
Vol 14 (131) ◽  
pp. 20170253 ◽  
Author(s):  
Ross D. Milton ◽  
Shelley D. Minteer
Keyword(s):  
Electron Transfer ◽  
Energy Conversion ◽  
Electrode Surface ◽  
Alternative Energy ◽  
Electronic Communication ◽  
Direct Electron Transfer ◽  
Electron Mediator ◽  
Important Chemical ◽  
Oxidoreductase Enzymes ◽  
Energy Conversion Devices

Enzymatic bioelectrocatalysis is being increasingly exploited to better understand oxidoreductase enzymes, to develop minimalistic yet specific biosensor platforms, and to develop alternative energy conversion devices and bioelectrosynthetic devices for the production of energy and/or important chemical commodities. In some cases, these enzymes are able to electronically communicate with an appropriately designed electrode surface without the requirement of an electron mediator to shuttle electrons between the enzyme and electrode. This phenomenon has been termed direct electron transfer or direct bioelectrocatalysis. While many thorough studies have extensively investigated this fascinating feat, it is sometimes difficult to differentiate desirable enzymatic bioelectrocatalysis from electrocatalysis deriving from inactivated enzyme that may have also released its catalytic cofactor. This article will review direct bioelectrocatalysis of several oxidoreductases, with an emphasis on experiments that provide support for direct bioelectrocatalysis versus denatured enzyme or dissociated cofactor. Finally, this review will conclude with a series of proposed control experiments that could be adopted to discern successful direct electronic communication of an enzyme from its denatured counterpart.

scholarly journals Nanocatalysts Containing Direct Electron Transfer-Capable Oxidoreductases: Recent Advances and Applications

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 9 ◽  
Author(s):  
Dalius Ratautas ◽  
Marius Dagys
Keyword(s):  
Electron Transfer ◽  
State Of The Art ◽  
Direct Electron Transfer ◽  
Biofuel Cells ◽  
Solid Surfaces ◽  
Electron Mediator ◽  
Research Directions ◽  
Catalytic Systems ◽  
Nanoparticle Catalysts ◽  
Nanoparticle Surface

Direct electron transfer (DET)-capable oxidoreductases are enzymes that have the ability to transfer/receive electrons directly to/from solid surfaces or nanomaterials, bypassing the need for an additional electron mediator. More than 100 enzymes are known to be capable of working in DET conditions; however, to this day, DET-capable enzymes have been mainly used in designing biofuel cells and biosensors. The rapid advance in (semi) conductive nanomaterial development provided new possibilities to create enzyme-nanoparticle catalysts utilizing properties of DET-capable enzymes and demonstrating catalytic processes never observed before. Briefly, such nanocatalysts combine several cathodic and anodic catalysis performing oxidoreductases into a single nanoparticle surface. Hereby, to the best of our knowledge, we present the first review concerning such nanocatalytic systems involving DET-capable oxidoreductases. We outlook the contemporary applications of DET-capable enzymes, present a principle of operation of nanocatalysts based on DET-capable oxidoreductases, provide a review of state-of-the-art (nano) catalytic systems that have been demonstrated using DET-capable oxidoreductases, and highlight common strategies and challenges that are usually associated with those type catalytic systems. Finally, we end this paper with the concluding discussion, where we present future perspectives and possible research directions.

Characterization of Mercaptoethylamine-Modified Gold Electrode Surface and Analyses of Direct Electron Transfer to Putidaredoxin

Langmuir ◽  
1995 ◽  
Vol 11 (12) ◽  
pp. 4818-4822 ◽  
Author(s):  
Ling Sang Wong ◽  
Vincent L. Vilker ◽  
William T. Yap ◽  
Vytas Reipa
Keyword(s):  
Electron Transfer ◽  
Electrode Surface ◽  
Gold Electrode ◽  
Direct Electron Transfer

scholarly journals Recent Advances in the Direct Electron Transfer-Enabled Enzymatic Fuel Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Sooyoun Yu ◽  
Nosang V. Myung
Keyword(s):  
Electron Transfer ◽  
Fuel Cell ◽  
Active Site ◽  
Electrode Surface ◽  
Oxidation Reaction ◽  
Direct Electron Transfer ◽  
Implantable Devices ◽  
Protein Matrix ◽  
Enzyme Active Site ◽  
Enzymatic Fuel Cell

Direct electron transfer (DET), which requires no mediator to shuttle electrons from enzyme active site to the electrode surface, minimizes complexity caused by the mediator and can further enable miniaturization for biocompatible and implantable devices. However, because the redox cofactors are typically deeply embedded in the protein matrix of the enzymes, electrons generated from oxidation reaction cannot easily transfer to the electrode surface. In this review, methods to improve the DET rate for enhancement of enzymatic fuel cell performances are summarized, with a focus on the more recent works (past 10 years). Finally, progress on the application of DET-enabled EFC to some biomedical and implantable devices are reported.

scholarly journals Direct Electron Transfer-Type Bioelectrocatalysis of Redox Enzymes at Nanostructured Electrodes

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 236 ◽  
Author(s):  
Taiki Adachi ◽  
Yuki Kitazumi ◽  
Osamu Shirai ◽  
Kenji Kano
Keyword(s):  
Electron Transfer ◽  
Protein Engineering ◽  
Electrode Surface ◽  
Direct Electron Transfer ◽  
Redox Enzymes ◽  
Type Reaction ◽  
The Past ◽  
Electrode Reactions ◽  
Basic Concepts ◽  
Catalytic Functions

Direct electron transfer (DET)-type bioelectrocatalysis, which couples the electrode reactions and catalytic functions of redox enzymes without any redox mediator, is one of the most intriguing subjects that has been studied over the past few decades in the field of bioelectrochemistry. In order to realize the DET-type bioelectrocatalysis and improve the performance, nanostructures of the electrode surface have to be carefully tuned for each enzyme. In addition, enzymes can also be tuned by the protein engineering approach for the DET-type reaction. This review summarizes the recent progresses in this field of the research while considering the importance of nanostructure of electrodes as well as redox enzymes. This review also describes the basic concepts and theoretical aspects of DET-type bioelectrocatalysis, the significance of nanostructures as scaffolds for DET-type reactions, protein engineering approaches for DET-type reactions, and concepts and facts of bidirectional DET-type reactions from a cross-disciplinary viewpoint.

Enzyme Electrochemistry — Biocatalysis on an Electrode

2006 ◽  
Vol 59 (4) ◽  
pp. 233 ◽  
Author(s):  
Paul V. Bernhardt
Keyword(s):  
Electron Transfer ◽  
Small Molecule ◽  
Electrode Surface ◽  
Catalytic Mechanism ◽  
Organic Substrates ◽  
Oxidation Reactions ◽  
Accurate Analysis ◽  
Practical Applications ◽  
Redox Partner ◽  
Oxidoreductase Enzymes

Oxidoreductase enzymes catalyze single- or multi-electron reduction/oxidation reactions of small molecule inorganic or organic substrates, and they are integral to a wide variety of biological processes including respiration, energy production, biosynthesis, metabolism, and detoxification. All redox enzymes require a natural redox partner such as an electron-transfer protein (e.g. cytochrome, ferredoxin, flavoprotein) or a small molecule cosubstrate (e.g. NAD(P)H, dioxygen) to sustain catalysis, in effect to balance the substrate/product redox half-reaction. In principle, the natural electron-transfer partner may be replaced by an electrochemical working electrode. One of the great strengths of this approach is that the rate of catalysis (equivalent to the observed electrochemical current) may be probed as a function of applied potential through linear sweep and cyclic voltammetry, and insight to the overall catalytic mechanism may be gained by a systematic electrochemical study coupled with theoretical analysis. In this review, the various approaches to enzyme electrochemistry will be discussed, including direct and indirect (mediated) experiments, and a brief coverage of the theory relevant to these techniques will be presented. The importance of immobilizing enzymes on the electrode surface will be presented and the variety of ways that this may be done will be reviewed. The importance of chemical modification of the electrode surface in ensuring an environment conducive to a stable and active enzyme capable of functioning natively will be illustrated. Fundamental research into electrochemically driven enzyme catalysis has led to some remarkable practical applications. The glucose oxidase enzyme electrode is a spectacularly successful application of enzyme electrochemistry. Biosensors based on this technology are used worldwide by sufferers of diabetes to provide rapid and accurate analysis of blood glucose concentrations. Other applications of enzyme electrochemistry are in the sensing of macromolecular complexation events such as antigen–antibody binding and DNA hybridization. The review will include a selection of enzymes that have been successfully investigated by electrochemistry and, where appropriate, discuss their development towards practical biotechnological applications.

scholarly journals Electrochemical Immunosensors with PQQ-Decorated Carbon Nanotubes as Signal Labels for Electrocatalytic Oxidation of Tris(2-carboxyethyl)phosphine

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1757
Author(s):  
Xiaohua Ma ◽  
Dehua Deng ◽  
Ning Xia ◽  
Yuanqiang Hao ◽  
Lin Liu
Keyword(s):  
Carbon Nanotubes ◽  
Electron Transfer ◽  
Direct Electron Transfer ◽  
Specific Antigen ◽  
Electrochemical Biosensors ◽  
Electron Mediator ◽  
High Turnover ◽  
Promising Alternative ◽  
Electrochemical Immunosensors ◽  
Sandwich Type

Nanocatalysts are a promising alternative to natural enzymes as the signal labels of electrochemical biosensors. However, the surface modification of nanocatalysts and sensor electrodes with recognition elements and blockers may form a barrier to direct electron transfer, thus limiting the application of nanocatalysts in electrochemical immunoassays. Electron mediators can accelerate the electron transfer between nanocatalysts and electrodes. Nevertheless, it is hard to simultaneously achieve fast electron exchange between nanocatalysts and redox mediators as well as substrates. This work presents a scheme for the design of electrochemical immunosensors with nanocatalysts as signal labels, in which pyrroloquinoline quinone (PQQ) is the redox-active center of the nanocatalyst. PQQ was decorated on the surface of carbon nanotubes to catalyze the electrochemical oxidation of tris(2-carboxyethyl)phosphine (TCEP) with ferrocenylmethanol (FcM) as the electron mediator. With prostate-specific antigen (PSA) as the model analyte, the detection limit of the sandwich-type immunosensor was found to be 5 pg/mL. The keys to success for this scheme are the slow chemical reaction between TCEP and ferricinum ions, and the high turnover frequency between ferricinum ions, PQQ. and TCEP. This work should be valuable for designing of novel nanolabels and nanocatalytic schemes for electrochemical biosensors.

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