scholarly journals Low-temperature kinetics of the reaction of oxygen and solubilized cytochrome oxidase

1978 ◽  
Vol 171 (3) ◽  
pp. 787-798 ◽  
Author(s):  
B Chance ◽  
C Saronio ◽  
J S Leigh ◽  
W J Ingledew ◽  
T E King
Keyword(s):  
Cytochrome Oxidase ◽  
Mixed Valence ◽  
Similar Species ◽  
Absorption Bands ◽  
Compound C ◽  
Valence States ◽  
Membrane Bound ◽  
Peroxy Compounds ◽  
Band Characteristic ◽  
Kinetics Of

The reaction of solubilized cytochrome oxidase in the fully reduced state with O2 at low temperatures reveals components with characteristics similar to those observed with the membrane-bound oxidase, namely compounds A and B, which are proposed to be ‘oxy’ and ‘peroxy’ compounds respectively. Similar species are identified in both solubilized and membrane-bound oxidases; the reaction velocity constant for the reation with O2 and the dissociation constant are decreased 2-3-fold in the solubilied preparation as compared with the membrane-bound species, owing to decreased reactivity towards O2 in the former. The oxidase prepared in the mixed-valence state shows the distinctive absorption band characteristic of compound C, identified in the membrane-bound oxidase. The assignment of the alpha, beta, gamma and near-i.r. absorption bands to possible valence states of these compounds is made.

scholarly journals The mechanism of reaction of ferricyanide-pretreated mixed-valence-state membrane-bound cytochrome oxidase with oxygen at 173 K

1978 ◽  
Vol 173 (3) ◽  
pp. 811-820 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Cytochrome Oxidase ◽  
Valence State ◽  
Linear Optimization ◽  
Mixed Valence ◽  
Mixed Valence State ◽  
Optical Wavelength ◽  
Valence States ◽  
Mechanism Of Reaction ◽  
Sequential Mechanism ◽  
Good Determination

1. The results of non-linear optimization studies on the mechanism of reaction of ferricyanide-pretreated mixed-valence-state cytochrome oxidase with O2 at 173 K are presented. The analysis is carried out on data obtained by means of dual-wavelength multi-channel spectroscopy at four wavelength pairs (444-463 nm, 604-630 nm, 608-630 nm and 830-940 nm) and at two O2 concentrations (360 micron and 520 micron). The only model that satisfies the triple requirement of a standard deviation within the standard error of the experimental data, a random distribution of residuals and good determination of the optimized parameters, is a three-intermediate sequential mechanism. 2. On the basis of the optimized values of the relative absorption coefficients of the intermediates at each wavelength obtained from the present paper together with data from optical wavelength scanning and e.p.r. spectroscopy obtained by low-temperature trapping studies, the possible valence states of the metal centres in each of the intermediates are discussed.

scholarly journals Studies on partially reduced mammalian cytochrome oxidase. Reactions with carbon monoxide and oxygen

1974 ◽  
Vol 137 (2) ◽  
pp. 205-215 ◽  
Author(s):  
Colin Greenwood ◽  
Michael T. Wilson ◽  
Maurizio Brunori
Keyword(s):  
Cytochrome Oxidase ◽  
Redox State ◽  
Mixed Valence ◽  
Order Rate Constant ◽  
Low Oxygen ◽  
Difference Spectra ◽  
Ferrocytochrome C ◽  
Kinetics Of ◽  
Enzyme Species ◽  
Binding Behaviour

A number of methods were used to prepare a species of mammalian cytochrome oxidase (EC 1.9.3.1, ferrocytochrome c–oxygen oxidoreductase) in which only cytochrome a3 is reduced and in combination with CO. The kinetics of CO binding by cytochrome a32+ in this species is significantly different from that exhibited by cytochrome a32+ in the fully reduced enzyme. The second-order rate constant for combination was 5X104m−1·s−1 and the ‘off’ constant was 3X10−2s−1. The kinetic difference spectra cytochrome a32+–cytochrome a32+–CO reveal further differences between the mixed-valence and the fully reduced enzyme. The reaction between cytochrome a32+ and oxygen in the mixed-valence species was followed in flow–flash experiments and reveals a fast, oxygen-dependent (8X107m−1·s−1 at low oxygen) rate followed by a slow process, whose rate is independent of oxygen but whose amplitude is dependent on [O2]. The fast oxygen-dependent reaction yields as the first product the so-called ‘oxygenated’ enzyme. We conclude from these experiments that the ligand-binding behaviour of cytochrome a3 depends on the redox state of its partners, a fact which represents clear evidence for site–site interaction in this enzyme. The fact that oxygen reacts rapidly with this enzyme species in which only one component, namely cytochrome a3, is reduced represents clear and unequivocal evidence that this is indeed the O2-binding site in cytochrome oxidase and may indicate that reduction of oxygen can proceed via single electron steps.

scholarly journals The mechanism of reaction of fully reduced membrane-bound cytochrome oxidase with oxygen at 176K

1978 ◽  
Vol 173 (3) ◽  
pp. 799-810 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Cytochrome Oxidase ◽  
Random Distribution ◽  
Linear Optimization ◽  
Valence States ◽  
Mechanism Of Reaction ◽  
Relative Absorption ◽  
Sequential Mechanism ◽  
Membrane Bound ◽  
Good Determination

1. The results of non-linear optimization studies on the mechanism of reaction of fully reduced cytochrome oxidase with O2 at 176K are presented. The analysis is carried out on data obtained by means of dual-wavelength multi-channel spectroscopy at three wavelength pairs (604-630, 608-630 and 830-940 nm) and at three O2 concentrations (60, 200 and 1180 micron). The only model that satisfies the triple requirement of a standard deviation within the standard error of the experimental data, good determination of the optimized parameters and a random distribution of residuals is a three-species sequential mechanism. 2. On the basis of the optimized values of the relative absorption coefficients of the intermediates at each wavelength obtained from the present paper together with data from low-temperature trapping, e.p.r. and magnetic-susceptibility studies, the possible valence states of the metal centres in each of the intermediates are discussed.

scholarly journals Oxygen kinetics of frozen cytochrome oxidase. The capacity of the oxygen pocket

1980 ◽  
Vol 185 (2) ◽  
pp. 527-530 ◽  
Author(s):  
K De Fonseka ◽  
B Chance
Keyword(s):  
Low Temperature ◽  
Cytochrome Oxidase ◽  
Limited Capacity ◽  
Oxygen Kinetics ◽  
Membrane Bound ◽  
Low Temperature Kinetics ◽  
The Difference ◽  
Kinetics Of

Low-temperature kinetics of the reaction between O2 and cytochrome oxidase suggest the existence of an O2 pocket of limited capacity in membrane-bound cytochrome oxidase, and one of larger capacity in purified cytochrome oxidase. A model is proposed to explain the difference in capacity of the pockets.

scholarly journals A new carbon monoxide-induced complex of cytochrome c oxidase

1978 ◽  
Vol 175 (3) ◽  
pp. 1147-1150 ◽  
Author(s):  
P Nicholls
Keyword(s):  
Carbon Monoxide ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mixed Valence ◽  
Difference Spectrum ◽  
Absorption Bands ◽  
Compound C

Cytochrome c oxidase isolated from ox heart forms a complex in the presence of millimolar concentrations of CO with absorption bands at 606, 565 and 435 nm (difference spectrum), distinct from both ferrocytochrome a and the classical 590nm carbon-monoxyferrocytochrome a3. This species, which closely resembles Compound C, the derivative formed on photolysis and oxygenation of mixed-valence cytochrome a3+a32+CO, may represent a cytochrome a32+CO complex in which the associated (‘invisible’) copper is still oxidized.

scholarly journals Low-temperature kinetics of the reactions of fully reduced membrane-bound cytochrome oxidase with oxygen in the Soret, α and near-infrared regions

1979 ◽  
Vol 177 (2) ◽  
pp. 613-621 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Magnetic Susceptibility ◽  
Low Temperature ◽  
Cytochrome Oxidase ◽  
Near Infrared ◽  
Optical Wavelength ◽  
Wavelength Scanning ◽  
Membrane Bound ◽  
Low Temperature Kinetics ◽  
Kinetics Of

The kinetics of the reaction of fully reduced membrane-bound cytochrome oxidase with O2 obtained in the Soret, alpha and near-i.r. regions were analysed, and the contributions of the three intermediates of the reaction [Clore & Chance (1978) Biochem. J. 173, 799–810] to seven wavelength pairs (430–463, 444–463, 590–630, 608–630, 740–940, 790–940 and 830–940 nm) were determined. The nature of the intermediates is discussed on the basis of the data in the present paper together with data in the literature from optical wavelength scanning, e.p.r., i.r. and magnetic-susceptibility studies.

scholarly journals Characterization of the intermediates in the reaction of membrane-bound mixed-valence-state cytochrome oxidase with oxygen at low temperatures by optical spectroscopy in the visible region

1980 ◽  
Vol 187 (3) ◽  
pp. 617-622 ◽  
Author(s):  
G M Clore
Keyword(s):  
Cytochrome Oxidase ◽  
Optical Spectroscopy ◽  
Valence State ◽  
Mixed Valence ◽  
Visible Region ◽  
Difference Spectrum ◽  
Difference Spectra ◽  
Mixed Valence State ◽  
Membrane Bound ◽  
The Difference

The ‘pure’ difference spectra of the three species, IM, IIM and IIIM, formed in the low-temperature reaction of membrane-bound mixed-valence-state cytochrome oxidase with O2 relative to unliganded membrane-bound mixed-valence-state cytochrome oxidase were characterized by optical spectroscopy in the visible region. The difference spectrum of species IM was characterized by a peak at 590 nm and a trough at 608 nm, that of species IIM by a peak at 606 nm, and that of species IIIM by a peak at 610 nm. A comparison with the difference spectra of species IIM and IIIM obtained with soluble cytochrome oxidase [Clore, Andréasson, Karlsson, Aasa & Malmström (1980) Biochem. J. 185, 155-167] revealed small but significant differences in the peak positions and bandwidths of the 605-610 nm absorption band.

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