Low Potential Catalytic Voltammetry of Human Sulfite Oxidase

Abstract

Highlights  Human sulfite oxidase (HSO) catalyses the oxidation of sulfite to sulfate.  Fe(III) hexa-amine complexes may act as synthetic electron acceptors from HSO.  Electrochemical sulfite oxidation can be achieved with HSO and the Fe(III) complexes.  Varying the Fe(III/II) redox potential of the mediators results in different voltammetry.  A sulfite biosensor is constructed and used to determine sulfite in wine and beer samples.

Mediated Catalytic Voltammetry of Holo and Heme‐Free Human Sulfite Oxidases

“…Very recently, we reported the catalytic voltammetry of holo HSO with the positively charged mediators bis(1,4,7‐triazacyclononane)iron(III) ([Fe(tacn) 2 ] 3+ ) and 1,2‐bis(1,4,7‐triaza‐1‐cyclononyl)‐ethane iron(III) ([Fe(dtne)] 3+ ) at a glassy carbon working electrode with HSO entrapped beneath a semi‐permeable membrane . Interestingly, we found that these positively charged mediators accumulated under the membrane in the presence of holo HSO and showed an enhanced redox response compared with a bare GC electrode.…”

“…The objective of simulation is to obtain values for the rate constants of the homogeneous reactions defined in Scheme that reproduce all voltammetric features over a range of sweep rates, substrate and mediators concentrations. Very recently, we simulated the mediated voltammetry of holo HSO with two positively charged mediators at a glassy carbon electrode . In that case, the mediators had the same overall charge and very similar structures but significantly different redox potentials.…”

“…The small peak‐to peak separation and the cathodically shifted Fe III/II redox couple are attributable to a strong association between the [Fe(dtne)] 3+ and HSO localized near the negatively charged heme domain leading to a response that is more consistent with a surface immobilized redox reaction. These results are consistent with our recent report for the electrochemistry of positively charged complexes with holo HSO at a glassy carbon electrode …”

“…As mentioned already, the pre‐wave corresponds to FM + molecules that are electrostatically attracted to holo HSO near the electrode surface. In other mediated electrochemical studies of Mo enzyme we have observed similar pre‐wave voltammetric responses …”

The 1,6,7,12‐Tetraazaperylene Bridging Ligand as an Electron Reservoir and Its Disulfonato Derivative as Redox Mediator in an Enzyme–Electrode Process

“…It should be noted that all inorganic redox mediators which have up to now been employed in voltammetric biosensors involve a metal‐centered redox process . In such devices cobalt complexes, ferrocenes, osmium and ruthenium complexes, ferricyanide as well as triazacyclononane iron complexes are used. In contrast, to the best of our knowledge, complex [ 4 ] 2+ is the first metal complex which shuttles the electron very well between an oxidase enzyme and an electrode in a voltammetric enzyme–electrode system by a redox‐active ligand.…”