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

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.

Zakharova, Galina S.Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (författare)
Poloznikov, Andrey A.Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (författare)
Calvente, Juan JoséUniversity of Seville (författare)
Hushpulian, Dmitry M.Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (författare)
Gorton, LoLund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)akem-lgo (författare)
Andreu, RafaelUniversity of Seville (författare)
University of SevilleDmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology (creator_code:org_t)

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