Biochemical and biophysical studies on cytochrome c oxidase XIV. The reaction with cytochrome c as studied by pulse radiolysis

Buuren, K.J.H. van; Gelder, B.F. Van; Wilting, Jaap; Braams, R.

doi:10.1016/0005-2728(74)90126-1

Cited by 61 publications

(18 citation statements)

References 34 publications

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“…The concentration of the enzyme was determined by absorption spectroscopy using either AA 55 onm (reduced minus oxidized) of 21.1 mM-1. cm-1 [18] or dA416 nm (reduced minus oxidized) of 57 mM -1 • cm -1 [19].…”

Section: Enzymementioning

confidence: 99%

“…The experimental set-up was as described before [19,20]. By variation of the pulse length (10-550 ns) and the pulse dose (50-1500 tad) the initial concentration of eaq-could be varied between 0.1 and 3 #M. The concentration of eaq-was always less than 10 ~ of that of cytochrome c.…”

Section: Pulse Radiolysismentioning

confidence: 99%

“…That such effects of charge interaction can be of importance is suggested by the very low reduction yield for the reaction of e~q-with the highly negatively charged cytochrome c oxidase molecule [19].…”

Section: Table IIImentioning

confidence: 99%

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The mechanism of reduction of cytochrome c as studied by pulse radiolysis

Wilting

Buuren

Braams

et al. 1975

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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SUMMARY1. The reaction of hydrated electrons with ferricytochrome c was studied using the pulse-radiolysis technique.2. In 3.3 mM phosphate buffer (pH 7.2), 100 mM methanol and at a concentration of cytochrome c of less than 20 #M the reduction kinetics of ferricytochrome c by hydrated electrons is a bimolecular process with a rate constant of 4.5 • 101 o M-t "s-1 (21 °C).3. At a concentration of cytochrome c of more than 20/~M the apparent order of the reaction of hydrated electrons with ferricytochrome c measured at 650 nm decreases due to the occurrence of a rate-determining first-order process with an estimated rate constant of 5 • 106 s-1 (pH 7.2, 21 °C).4. At high concentrations of cytochrome c the reaction-time courses measured at 580 and 695 nm appear to be biphasic. A rapid initial phase (75 ~ and 30 ~ of total absorbance change at 580 and 695 nm, respectively), corresponding to the reduction reaction, is followed by a first-order change in absorbance with a rate constant of 1.3 • l0 s s -1 (pH 7.2, 21 °C).5. The results are interpreted in a scheme in which first a transient complex between cytochrome c and the hydrated electron is formed, after which the heme iron is reduced and followed by relaxation of the protein from its oxidized to its reduced conformation.

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Section: Enzymementioning

confidence: 99%

Section: Pulse Radiolysismentioning

confidence: 99%

See 1 more Smart Citation

The mechanism of reduction of cytochrome c as studied by pulse radiolysis

Wilting

Buuren

Braams

et al. 1975

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…The reactions are extremely rapid: rate constants approaching the diffusion-limited values of 10" M-' s-' are obtained at pl~ysiological pH values in the case of cytochrome c. In fact, hydrated electrons will radicalize nearly any organic substance, which in turn can react rapidly with cytochronle c, causing its reduction [ 11. In pulse radiolysis studies of cytochrome oxidase, 2.45 PM hydrated electrons are produced of which -50% or 1 .15 PM react with 1 .15 PM cytochrome oxidase in a half-time of 3.7 ps [5]. In synchrotron radiation studies, usual beam intensities at the sample (-6 X 10" pIlotons~s) are calculated to give -2.5 PM hydrated electrons/s.…”

Section: Introductionmentioning

confidence: 99%

Identifiction and assay of synchrotron radiation‐induced alterations on metalloenzymes and proteins

et al. 1980

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“…Recent kinetic studies on mammalian cytochrome oxidase have been aimed at the isolation of individual steps and the identification of intermediates involved in catalysis (1)(2)(3). Presteady-state measurements have so far been performed mainly on the reaction of the fully or partially oxidized enzyme with reduced cytochrome c, under aerobic or anaerobic conditions, and on the reaction of the fully reduced enzyme with oxygen (4)(5)(6)(7)(8).…”

mentioning

confidence: 99%