pH changes associated with cytochrome c oxidase reaction with H2O2 Protonation state of the peroxy and oxoferryl intermediates

Konstantinov, Alexander A.; Capitanio, Nazzareno; Vygodina, Tatiana V.; Papa, Sergio

doi:10.1016/0014-5793(92)81412-f

Cited by 31 publications

(33 citation statements)

References 21 publications

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“…However, if m = 1, as found in [34,35], then n can be as high as 1.5, directly confirming the conclusion [13] that conversion of F to Ox is characterized by a charge translocated per e-stoichiometry higher than 1. Nevertheless, this value is still less than PZ = 2 implied by the scheme suggested in [2].…”

Section: Febs Letterssupporting

confidence: 77%

Flash‐induced membrane potential generation by cytochrome c oxidase

et al. 1993

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Flash‐induced single‐electron reduction of cytochrome c oxidase. Compound F (oxoferryl state) by RuII(2,2'‐bipyridyl)2+ 3 [Nilsson (1992) Proc. Natl. Acad. Sci. USA 89, 6497‐6501] gives rise to three phases of membrane potential generation in proteoliposomes with τ values and contributions of ca. 45 μs (20%), 1 ms (20%) and 5 ms (60%). The rapid phase is not sensitive to the binuclear centre ligands, such as cyanide or peroxide, and is assigned to vectorial electron transfer from CuA to heme a. The two slow phases kinetically match reoxidation of heme a, require added H2O2 or methyl peroxide for full development, and are completely inhibited by cyanide; evidently, they are associated with the reduction of Compound F to the Ox state by heme a. The charge transfer steps associated with the F to Ox conversion are likely to comprise (i) electrogenic uptake of a ‘chemical’ proton from the N phase required for protonation of the reduced oxygen atom and (ii) electrogenic H+ pumping across the membrane linked to the F to Ox transition. Assuming heme a ‘electrical location’ in the middle of the dielectric barrier, the ratio of the rapid to slow electrogenic phase amplitudes indicates that the F to Ox transition is linked to transmembrane translocation of 1.5 charges (protons) in addition to an electrogenic uptake of one ‘chemical’ proton required to form Fe3+‐OH− from Fe4+ = O2−. The shortfall in the number of pumped protons and the biphasic kinetics of the millisecond part of the electric response matching biphasic reoxidation of heme a may indicate the presence of 2 forms of Compound F, reduction of only one of which being linked to full proton pumping.

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Section: Febs Letterssupporting

confidence: 77%

Flash‐induced membrane potential generation by cytochrome c oxidase

et al. 1993

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“…The CcO/H 2 O 2 reaction has been a conundrum and subject of debate for a number of years (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). The reaction serves as an alternative view of the peroxy (2e Ϫ ) oxidation level.…”

mentioning

confidence: 99%

Direct Detection of Fe(IV)=O Intermediates in the Cytochrome aa3 Oxidase from Paracoccus denitrificans/H2O2 Reaction

Pinakoulaki

Pfitzner

Ludwig

et al. 2003

Journal of Biological Chemistry

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We report the first evidence for the formation of the "607-and 580-nm forms" in the cytochrome oxidase aa 3 / H 2 O 2 reaction without the involvement of tyrosine 280. The pK a of the 607-580-nm transition is 7.5. The 607-nm form is also formed in the mixed valence cytochrome oxidase/O 2 reaction in the absence of tyrosine 280. Steady-state resonance Raman characterization of the reaction products of both the wild-type and Y280H cytochrome aa 3 from Paracoccus denitrificans indicate the formation of six-coordinate low spin species, and do not support, in contrast to previous reports, the formation of a porphyrin -cation radical. We observe three oxygen isotope-sensitive Raman bands in the oxidized wildtype aa 3 /H 2 O 2 reaction at 804, 790, and 358 cm ؊1 . The former two are assigned to the Fe(IV)‫؍‬O stretching mode of the 607-and 580-nm forms, respectively. The 14 cm ؊1 frequency difference between the oxoferryl species is attributed to variations in the basicity of the proximal to heme a 3 His-411, induced by the oxoferryl conformations of the heme a 3 -Cu B pocket during the 607-580-nm transition. We suggest that the 804 -790 cm ؊1 oxoferryl transition triggers distal conformational changes that are subsequently communicated to the proximal His-411 heme a 3 site. The 358 cm ؊1 mode has been found for the first time to accumulate with the 804 cm ؊1 mode in the peroxide reaction. These results indicate that the mechanism of oxygen reduction must be reexamined.

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“…The calculated bimolecular rate constant of 2.6 M –1 s –1 for superoxide generation from these data is in a good agreement with the published value of 2–4 M –1 s –1 . 35 …”

Section: Resultsmentioning

confidence: 99%

“…24,30,34,35 According to this proposal, free H 2 O 2 acts as a one-electron donor for the transition of P to F or even for the conversion of F to O . 30 The two superoxide anions expected to be formed in transitions of P to F and F to O are released and subsequently dismute to peroxide and O 2 .…”

Section: Discussionmentioning

confidence: 99%

“…In the presence of excess peroxide, the enzyme shows the ability to continually decrease the concentration of H 2 O 2 by turnover, even in the absence of external electron donors. 30 In the course of this turnover, the release of molecular oxygen (O 2 ), 31−33 superoxide, 34,35 and hydroxyl radicals 36 has been observed. Moreover, CcO exposed to peroxide showed various sites of oxidative modifications and a decline in catalytic activity.…”

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confidence: 99%

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How Hydrogen Peroxide Is Metabolized by Oxidized Cytochrome c Oxidase

et al. 2014

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In the absence of external electron donors, oxidized bovine cytochrome c oxidase (CcO) exhibits the ability to decompose excess H2O2. Depending on the concentration of peroxide, two mechanisms of degradation were identified. At submillimolar peroxide concentrations, decomposition proceeds with virtually no production of superoxide and oxygen. In contrast, in the millimolar H2O2 concentration range, CcO generates superoxide from peroxide. At submillimolar concentrations, the decomposition of H2O2 occurs at least at two sites. One is the catalytic heme a3–CuB center where H2O2 is reduced to water. During the interaction of the enzyme with H2O2, this center cycles back to oxidized CcO via the intermediate presence of two oxoferryl states. We show that at pH 8.0 two molecules of H2O2 react with the catalytic center accomplishing one cycle. In addition, the reactions at the heme a3–CuB center generate the surface-exposed lipid-based radical(s) that participates in the decomposition of peroxide. It is also found that the irreversible decline of the catalytic activity of the enzyme treated with submillimolar H2O2 concentrations results specifically from the decrease in the rate of electron transfer from heme a to the heme a3–CuB center during the reductive phase of the catalytic cycle. The rates of electron transfer from ferrocytochrome c to heme a and the kinetics of the oxidation of the fully reduced CcO with O2 were not affected in the peroxide-modified CcO.

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pH changes associated with cytochrome c oxidase reaction with H₂O₂ Protonation state of the peroxy and oxoferryl intermediates

Cited by 31 publications

References 21 publications

Flash‐induced membrane potential generation by cytochrome c oxidase

Flash‐induced membrane potential generation by cytochrome c oxidase

Direct Detection of Fe(IV)=O Intermediates in the Cytochrome aa3 Oxidase from Paracoccus denitrificans/H2O2 Reaction

How Hydrogen Peroxide Is Metabolized by Oxidized Cytochrome c Oxidase

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