The Fe (III)/Fe(II) redox couple as a probe of immobilized tobacco peroxidase: Effect of the immobilization protocol

Research output: Contribution to journalArticle

Abstract

Non-turnover voltammetry is a sensitive tool to characterize the electrochemical properties of redox proteins. However, the catalytically competent oxidation states of most peroxidases do not display the required electrochemical reversibility. In this report, we circumvent this limitation and exploit the voltammetric response associated with the Fe(III)/Fe(II) redox couple of tobacco peroxidase to probe the energetics and electronic connectivity of the heme pocket. We have applied this approach to rationalize the previously reported influence of the immobilization protocol on the electrocatalytic activity of tobacco peroxidase. To decouple proton and electron transfer steps, measurements have been carried out over the 3 ≤ pH ≤ 9 range and a 1e/2H+ ladder scheme has been adopted for their analysis. At each pH, thermodynamic and kinetic parameters associated with the Fe(III)/Fe(II) redox conversion were determined as a function of temperature in the 0-30 °C range. Reduction entropies and reorganization energies displayed different values for covalently immobilized and physisorbed enzymes, pointing to a larger involvement of the solvent in the last case. These findings, together with a larger electronic coupling between the prosthetic group and the electrode, are indicative of a partial denaturation of the physisorbed enzymes as the origin of their lower electrocatalytic activity.

Details

Authors
  • José Luis Olloqui-Sariego
  • Galina S. Zakharova
  • Andrey A. Poloznikov
  • Juan José Calvente
  • Dmitry M. Hushpulian
  • Lo Gorton
  • Rafael Andreu
Organisations
External organisations
  • University of Seville
  • Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Medicinal Chemistry

Keywords

  • Fe(III)/Fe(II) couple, Immobilization protocol, Proton coupled electron transfer, Thermodynamics and kinetics, Tobacco peroxidase
Original languageEnglish
Pages (from-to)55-61
Number of pages7
JournalElectrochimica Acta
Volume299
Publication statusPublished - 2019
Publication categoryResearch
Peer-reviewedYes