The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active

Spricigo, Roberto; Leimkühler, Silke; Gorton, Lo; Scheller, Frieder W.; Wollenberger, Ulla

doi:10.1002/ejic.201500034

Cited by 5 publications

(9 citation statements)

References 36 publications

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“…These steps involve a repositioning of the domains to reduce electron transfer distances permitting electron transfer from Mo to Fe of SO‐HD and to cytochrome c . A reaction with soluble and polymer bound redox mediators is also possible . Direct unmediated electron transfer from the reduced enzyme to electrodes proceeds via the heme domain .…”

Section: Introductionmentioning

confidence: 99%

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

et al. 2016

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1Introduction Molybdenum (Mo) containing enzymes have been associated with the catalysis of important reactions in the metabolism of smallm oleculess uch as carbon nitrogen, and sulfur [1a, b].T he sulfite oxidizing enzymes sulfite oxidase (SO) and sulfite dehydrogenase (SDH) catalyze the oxidation of sulfite to sulfate accompaniedw ith the release of two electrons and two protons according to the following equation:All sulfite oxidizing enzymes share the same catalytic Mo cofactor (Moco) containingu nit. But the number and type of additional redoxc enters differb etween enzymes from different classes of organisms, which has an impact on the type of electrona cceptor the enzyme can use [2a, b].O nly in the vertebrate SO ah eme b binding domaini sc ovalently linkedt ot he core structure of the enzyme.T he human sulfite oxidase (hSO) shows al arge structural homology to the enzyme from chicken liver (cSO) which is ad imeric enzyme where each subunit of the homodimer consists of an N-terminal heme b binding domain( SO-HD), followed by ap olypeptide tetherc onnectingt he heme domain to the Moco-containing domain (SO-MD) and ad imerization domain at the C-terminus [3].Thes ingle steps of the SO catalyzed reaction involve the two-electron oxidationo fs ulfite to sulfate at the Moco center, where Mo VI is reduced to Mo IV .I nv ertebrate SO the Mo VI regeneration is naturally coupled to the reduction of two equivalents of soluble cytochrome c which proceeds in two subsequent intra-and intermolecular singlee lectron transfer steps via the heme b5 containing site [4a, b, c].T hese steps involve ar epositioning of the domains to reduce electron transfer distances permitting electron transfer from Mo to Fe of SO-HD and to cytochrome c [5a, b].Areaction with soluble [6a, b] and polymerb ound redoxm ediators is also possible [7a, b]. Direct unmediated electron transfer from the reduced enzyme to electrodes proceedsv ia the hemed omain [8]. This process was most effective when the enzymei si mmobilized on electrode surfaces modified with positive charged SAMs facilitating the oriented assembly of SO electron transfer and bioelectrocatalysis [9a, b].Abstract:W er eport efficient bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) immobilizedo n ag old nanoparticle (AuNP)m odified gold electrode.T he AuNP were synthesized in aqueous phase by using branched polyethyleneimine (PEI) as reducing as well as stabilizing agent. Golde lectrodes were modified by as elf assembled monolayer of dithio-bis(N-hydroxysuccinimidyl propionate) (DTSP) onto which the NP and hSO were immobilized. Cyclic voltammetry of the hSO modified electrode in the absence of substrater evealedaquasi-reversible direct electrochemical reactiono ft he heme domaino fhSO with fast electron transfer rate.T he electron transferr ate constant of k s = 32 s À1 and the formal potential E 0 ' = À0.155 Vv s. Ag/AgCl/1 MK Cl were estimated. Comparatives tudies with nanoparticles of BaSO 4 indicate the importance of the NP conductivity for charge transfer an...

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Section: Introductionmentioning

confidence: 99%

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

et al. 2016

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“…This reinforces the point that the negatively charged heme domain of holo HSO is more strongly attracted to the positively charged [Fe(dtne)] 3+ mediator and this enhances the catalytic response by facilitating effective electron transfer and lowering the catalytic potential. A similar observation reported for the catalytic voltammetry of holo and heme‐free HSOs with a positively charged osmium complex at a carbon electrode found that the catalytic response of heme‐free HSO was only 30% relative to that from holo HSO …”

Section: Resultsmentioning

confidence: 99%

“…Apparent Michaels constants ( K M,sulfite ) of 747 μM and 676 μM were obtained from the Michaelis–Menten plot (current taken at +480 mV) for holo HSO and heme‐free HSO electrodes, respectively (Supporting Information, Figure S4). The observed K m value is almost same at holo and heme‐free HSO electrodes and it is consistent with a recent report on electrochemistry of HSO with the polymeric positively charged mediator poly(vinylpyridine)‐[osmium‐(N,N′‐methyl‐2,2′‐biimidazole) 3 ] 3+/2+ , which found an apparent K M value of 500 and 450 μM for heme‐free and Holo HSO, respectively. Conversely, the observed K M value is very high compared to the value reported from solution assay ( K m =9 μM) for holo HSO with its physiological electron acceptor cytochrome c .…”

Section: Resultsmentioning

confidence: 99%

“…The efficiency of mediated electron transfer mainly depends both on the thermodynamic driving force i. e. the difference between the formal potentials of the enzyme redox cofactor and the mediator, and the distance between the two redox centers. The Mo domain of HSO may undergo electron transfer with its natural electron acceptor cyt c and also with synthetic electron acceptor osmium complexes . However, the overall rate of sulfite oxidation was very slow at the (heme‐free) Mo domain of a HSO modified electrode relative to holo HSO.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Herein, we report the electrocatalytic voltammetry of holo and heme‐free human sulfite oxidase (HSO) mediated by the synthetic iron complexes 1,2‐bis(1,4,7‐triaza‐1‐cyclononyl)ethane iron(III) bromide, ([Fe(dtne)]Br3.3H2O), potassium ferricyanide (K3[Fe(CN)6]), and ferrocene methanol (FM) at a 5‐(4′‐pyridinyl)‐1,3,4‐oxadiazole‐2‐thiol (Hpyt) modified gold working electrode. Holo HSO contains two electroactive redox cofactors, comprising a mostly negatively charged cyt b5 (heme) domain and a Mo cofactor (Moco) domain (the site of sulfite oxidation), where the surface near the active site is positively charged. We anticipated different catalytic voltammetry based on either repulsive or attractive electrostatic interactions between the holo or heme‐free enzymes and the positively or negatively charged redox mediators. Both holo and heme‐free HSO experimental catalytic voltammetry has been modeled by using electrochemical simulation across a range of sweep rates and concentrations of substrate and both positive and negatively charged electron acceptors ([Fe(dtne)]3+, [Fe(CN)6]3− and FM+), which provides new insights into the kinetics of the HSO catalytic mechanism. These mediator complexes have almost the same redox potential (all lying in the range +415 to +430 mV vs. NHE) and, thus, deliver the same driving force for electron transfer with the Mo cofactor. However, differences in the electrostatic affinities between HSO and the mediator have a significant influence on the electrocatalytic response.

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“…32,44 Graphite electrodes have been used for the immobilization of hSO. 23,44,45 However, there are no reports on employing graphene to achieve DET between hSO and the electrodes.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Sulfite Oxidase Bioanodes Based on Graphene Functionalized Carbon Paper for Sulfite/O₂ Biofuel Cells

et al. 2019

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The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active

Cited by 5 publications

References 36 publications

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

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

Three-Dimensional Sulfite Oxidase Bioanodes Based on Graphene Functionalized Carbon Paper for Sulfite/O₂ Biofuel Cells

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The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active

Cited by 5 publications

References 36 publications

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase

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

Three-Dimensional Sulfite Oxidase Bioanodes Based on Graphene Functionalized Carbon Paper for Sulfite/O2 Biofuel Cells

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Product

Resources

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Three-Dimensional Sulfite Oxidase Bioanodes Based on Graphene Functionalized Carbon Paper for Sulfite/O₂ Biofuel Cells