Direct spectrophotometric studies of the kinetics of oxidation and reduction of ubiquinone of heart-muscle particles

Chance, Britton; Redfearn, E.R.

doi:10.1042/bj0800632

Cited by 67 publications

(14 citation statements)

References 21 publications

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“…The concentration of water-soluble proteins was determined by the Biuret method (Chance & Redfearn, 1961;Copeland, 1994), using an UV Mini 1240 spectrophotometer (Shimadzu; Carnaxide, Portugal). The Biuret colour yield was standardised against an aqueous solution of analytical bovine serum albumin (Sigma-Aldrich) covering the range 110 mg/ml.…”

Section: Assessment Of Proteinsmentioning

confidence: 99%

Characterisation of high added value compounds in wastewater throughout the salting process of codfish (Gadus morhua)

et al. 2011

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Section: Assessment Of Proteinsmentioning

confidence: 99%

Characterisation of high added value compounds in wastewater throughout the salting process of codfish (Gadus morhua)

et al. 2011

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“…Fast changes were displayed on a storage oscilloscope and photographed to give permanent records; slow changes were displayed on a pen recorder chart. Ubiquinone was monitored wiith the wavelength pair 275 to 290 my or 282 to 295 mMu (17,39). For cytochrome c, the pair 549 to 540 my was used.…”

Section: Methodsmentioning

confidence: 99%

The Respiratory Chain of Plant Mitochondria. I. Electron Transport Between Succinate and Oxygen in Skunk Cabbage Mitochondria

Storey

Bahr

1969

Plant Physiol.

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A bstract. The kinetics of oxidation of ubiquinone, flavoprotein, cytochrome c, and the cytochrome b complex in skunk cabbage (Symplocarpus foetidus) mitochondria made anaerobic with succinate have been measured spectrophotometrically and fluorimetrically in the absence of respiratory inhibitor and in the presence of cyanide or antimycin A. No component identifiab,le by these means was oxidized rapidly enough in the presence of one or the other inhibitor to qualify for the role of alternate oxidase. Cycles of oxidation and rereduction of flavoprotein and ubiquinone obtained by injecting 12 jM oxygen into the anaerobic mitochondrial suspension were kinetically indistinguishable in the presence of cyanide or antimycin A, implying that these 2 components are part of a respiratory pathwav between succinate and oxygen which does not involve the cytochromes and does involve a cyanide-insensitive alternate oxidase. The cytochrome b complex shows biphasic oxidation kinetics with half times of 0.018 sec and 0.4 sec in the absence of inhibitor, which increase to 0.2 sec and 1 sec in the presence of cyanide. In the presence of antimycin A, the oxidation of the cytochrome b complex shows an induction period of 1 sec and *a half-time of 3.5 sec. A split respiratory chain with 2 terminal oxidases and a branch point between the cytochromes and flavoprotein and ubiquinone is proposed for these mitochondria.Many plant tissues yield mitochondria whose rate of respiration is partiallv insensitive to inhibition by cvanide (34.42). The most notable of such tissues are the spadices of the flowers of Arum maculatum (1, 2) and the skuinik cabbage. Symplocarpus foetidus (3,28, 299). Mitochondria isolated from these tissues are often totally insensitive to respiratory inhibition by cyanide or antimycin A. The cvtochromes of skunk cabbage mitochondria have been characterized by their spectra (4,16,19)

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“…As expressed by Equation ( i ) , only part (Qa) of the total Q (Qt) is reducible even under equilibrium conditions in the presence of KCN and substrate [13,15], so that Qt is divided up into an active part ( Qa) and an inactive part (Qi) : Qt = Qa + Qi. (1) Qi varies between 10 and 20°/, of Qi, it depends on the particle preparations and increases with the age of the submitochondrial particles. In the following equations only the redox state of Qa is considered.…”

Section: -60 "C) I N These Extracts Oxidized Q (Qox + Qi)mentioning

confidence: 99%

The Kinetics of the Redox Reactions of Ubiquinone Related to the Electron‐Transport Activity in the Respiratory Chain

Kröger

Klingenberg

1973

European Journal of Biochemistry

338

112

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The role of ubiquinone (Q) in the respiratory chain is quantitatively analyzed by correlating both the steady-state redox level of Q and the kinetics of oxidation and reduction with the flux of the overall electron transport in uncoupled submitochondrial particles. This is achieved by experimentally defining donor and acceptor activities for Q.1. The degree of reduction of Q in the steady state is proportional to the respiratory activity with NADH and succinate, if the respiratory activity is varied by titrating the donor side for Q with rotenone and malonate, respectively. The proportionality constant (acceptor activity, Vex) is independent of the substrate used. .The degree of oxidation of Q in the steady state is proportional to the respiratory activity as varied by titration of the acceptor side for Q with antimycin. The proportionality constant (donor activity, V r e d ) is independent of the acceptor activity and depends on the dehydrogenase activity for NADH and succinate.3. From these experimental relations, the redox state of Q in the steady state and the respiratory activity can be described as functions of the donor and the acceptor activity only. The equations are valid with both NADH and succinate as the substrates. 4.The kinetics of oxidation of Q on the addition of oxygen as measured by the quench-flow method are in agreement with that measured by direct absorption recording in a mixing chamber. The reaction is first order with a rate constant equal to the acceptor activity divided by the amount of redox-active Q ( VOx/&&). The final steady-state level (in the present case 15O/, reduction) is a result also of the reduction reaction with the first-order rate constant, Vr,d/Qa. 5 . The acceptor activity can also be measured as maximum respiratory activity with durohydroquinone. This activity is independent of the presence of Q but sensitive to antimycin.Thus, the acceptor activity for ubiquinone can be measured by three independent methods. 6. It is concluded, that also in the steady state the reduction and oxidation of the active Q-pool follow pseudo-first-order reactions, the rates of which are equal to the respiratory rate.The total amount of redox-active Q is kinetically and functionally homogeneous and is not divided into substrate-specific compartments.The relation between the kinetics of the redox reactions of the mitochondria1 Q and its function in electron transport has been considered so far only in qualitative terms and contradicting conclusions were drawn from these studies. MATERIALS AND METHODS Preparation of Submitochondrial ParticlesSubmitochondrial particles were prepared by sonication of beef heart mitochondria. 5 m l of the mitochondrial suspension containing 20 mg/ml protein were sonicated six times for 5 s at 0-5 "C with the Branson sonifier, model J17V (Danbury, Connecticut, U.S.A.), a t maximal energy. Normal submitochondrial particles were obtained by sonication in 0.3 M sucrose, submitochondrial particles supplemented with cytochrome c with further addition of 0.3 mg/ml cy...

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Direct spectrophotometric studies of the kinetics of oxidation and reduction of ubiquinone of heart-muscle particles

Cited by 67 publications

References 21 publications

Characterisation of high added value compounds in wastewater throughout the salting process of codfish (Gadus morhua)

Characterisation of high added value compounds in wastewater throughout the salting process of codfish (Gadus morhua)

The Respiratory Chain of Plant Mitochondria. I. Electron Transport Between Succinate and Oxygen in Skunk Cabbage Mitochondria

The Kinetics of the Redox Reactions of Ubiquinone Related to the Electron‐Transport Activity in the Respiratory Chain

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