Influence of tryptophan mutation on the direct electron transfer of immobilized tobacco peroxidase

• Published in: Electrochimica acta Vol. 351; p. 136465
• Main Authors: Olloqui-Sariego, José Luis, Zakharova, Galina S., Poloznikov, Andrey A., Calvente, Juan José, Hushpulian, Dmitry M., Gorton, Lo, Andreu, Rafael
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10-08-2020; Elsevier BV
• Subjects: Chemical Sciences; Coupling (molecular); Direct electron transfer; Electrodes; Electron transfer; Electrons; Hydrogen peroxide; Kemi; Leucine; Molecular structure; Mutation; Mutations; Natural Sciences; Naturvetenskap; Peroxidase; Proteins; Teoretisk kemi; Theoretical Chemistry; Tobacco; Tobacco peroxidase; Tryptophan; Tryptophan; Mutations; Direct electron transfer; Tobacco peroxidase
• DOI: 10.1016/j.electacta.2020.136465
• EISSN: 1873-3859
• ISSN: 0013-4686

A major challenge in the design of electrochemical biodevices is to achieve fast rates of electron exchange between proteins and electrodes. In this work, we show that a significant increase in the direct electron transfer rate between a graphite electrode and Tobacco Peroxidase takes place when a surface exposed leucine, located in the vicinity of the heme pocket, is replaced by tryptophan. The analysis of the Fe(III)/Fe(II) voltammetric responses of native and mutated proteins, as a function of solution pH and temperature, leads to similar values of the reduction entropy and reorganization energy, but to a higher electronic coupling in the case of the mutant. In addition, the mutated and native proteins are shown to display similar electrocatalytic activities to reduce hydrogen peroxide at positive potentials, indicating that the molecular structure of the heme pocket is largely unaffected by the mutation.
•Replacement leucine by tryptophan leads to an increase of the electron transfer rate of the Fe(III)/Fe(II) redox couple.•Charge transfer thermodynamic and kinetic parameters are obtained as a function of temperature and pH.•Reduction entropies and reorganization energies are similar for native and mutated enzymes.•The electronic coupling between heme and electrode increases for the mutated protein.