Cookies help us deliver our services. By using our services, you agree to our use of cookies. More information

Difference between revisions of "Residual oxygen consumption"

From Bioblast
Line 26: Line 26:
::::* '''Previous editions''' (including [[Gnaiger 2014 MitoPathways]]): Mitochondrial respiration is frequently corrected for ROX, then  distinguishing '''ROX-corrected''' [[ROUTINE]], [[LEAK]], [[OXPHOS]] or [[ETS]] (''R'', ''L'', ''P'' and ''E'') from the corresponding '''apparent''' fluxes that have not been corrected for ROX . ''Apparent'' fluxes (not corrected for ROX; ''R''´, ''L''´, ''P''´ and ''E''´) places the terminology into the conceptual context of physical chemistry (including kinetics), where e.g. apparent equilibrium constants, ''K''<sub>eq</sub>´ (apparent Michaelis-Menten kinetic constants, ''K''<sub>m</sub>´) are carefully  distinguished from the less accessible (or inaccessible) 'true' constants, ''K''<sub>eq</sub> (''K''<sub>m</sub>).
::::* '''Previous editions''' (including [[Gnaiger 2014 MitoPathways]]): Mitochondrial respiration is frequently corrected for ROX, then  distinguishing '''ROX-corrected''' [[ROUTINE]], [[LEAK]], [[OXPHOS]] or [[ETS]] (''R'', ''L'', ''P'' and ''E'') from the corresponding '''apparent''' fluxes that have not been corrected for ROX . ''Apparent'' fluxes (not corrected for ROX; ''R''´, ''L''´, ''P''´ and ''E''´) places the terminology into the conceptual context of physical chemistry (including kinetics), where e.g. apparent equilibrium constants, ''K''<sub>eq</sub>´ (apparent Michaelis-Menten kinetic constants, ''K''<sub>m</sub>´) are carefully  distinguished from the less accessible (or inaccessible) 'true' constants, ''K''<sub>eq</sub> (''K''<sub>m</sub>).


::::* '''Mitochondrial physiology nomenclature''': Despite the fact that the previously used nomenclature provides a conceptually consistent framework of physical chemistry, generalized applicability may gain from a shift to a pragmatic emphasis of the experimental context of mitochondrial physiology. ROX correction is a baseline correction, which may be evaluated by a direct measurement within an experimental assay, or by independent test experiments for critical evaluation of the best estimate for a particular ROX correction. The ROX correction, therefore, may be emphasized by labelling the ROX-corrected values as 'true' mitochondrial (mt) fluxes [''R''(mt), ''L''(mt), ''P''(mt) and ''E''(mt)]. Unfortunately, the total ''R'', ''L'', ''P'' and ''E'' values in this mitochondrial physiology system carry opposite meanings to the physical chemistry system of terminology. Agreement is required for paving the way towards consistent data reporting and managing a meaningful database (but agreement is not even reached in hot debates on caloric units [J versus cal] or commonly used temperature scales [°C versus Faraday].
::::* '''Mitochondrial physiology nomenclature''': Despite the fact that the previously used nomenclature provides a conceptually consistent framework of physical chemistry, generalized applicability may gain from a shift to a pragmatic emphasis of the experimental context of mitochondrial physiology. ROX correction is a baseline correction, which may be evaluated by a direct measurement within an experimental assay, or by independent test experiments for critical evaluation of the best estimate for a particular ROX correction. The ROX correction, therefore, may be emphasized by labelling the ROX-corrected values as 'true' mitochondrial (mt) fluxes [''R''(mt), ''L''(mt), ''P''(mt) and ''E''(mt)]. Unfortunately, the total ''R'', ''L'', ''P'' and ''E'' values in this mitochondrial physiology system carry opposite meanings to the physical chemistry system of terminology. Agreement is required for paving the way towards consistent data reporting and managing a meaningful database (but agreement is not even reached in hot debates on caloric units [J versus cal] or frozen debates on commonly used temperature scales [°C versus Faraday].





Revision as of 23:07, 2 November 2016


high-resolution terminology - matching measurements at high-resolution


Residual oxygen consumption

Description

ROX.jpg Residual oxygen consumption, ROX, is the respiration due to oxidative side reactions remaining after application of ETS inhibitors to mitochondrial preparations or cells, or in mt-preparations incubated without addition of fuel substrates (in the presence of ADP following a stimulation of the consumption of endogenous fuel substrates: State 2). Different conditions designated as ROX states (different combinations of inhibitors of CI, CII, CIII and CIV; or respiration of mt-preparations without addition of fuel substrates) may result in consistent or significantly different levels of oxygen consumption. Hence the best quantitative estimate of ROX has to be carefully evaluated. Mitochondrial respiration is frequently corrected for ROX, then distinguishing total ROUTINE, LEAK, OXPHOS or ETS (R, L, P and E) respiration from the corresponding ROX-corrected, mitochondrial (ETS-linked) fluxes [R(mt), L(mt), P(mt) and E(mt)]. When expressing ROX as a fraction of ETS capacity (flux control ratio), total flux, E (not corrected for ROX), should be taken as the reference. ROX may be related to, but is of course different from ROS production. » MiPNet article

Abbreviation: ROX

Reference: Gnaiger 2014 MitoPathways, Gnaiger 2009 Int J Biochem Cell Biol

ROX or non-mitochondrial respiration and potential artefacts

Publications in the MiPMap
Gnaiger E (2016) ROX or non-mitochondrial respiration and potential artefacts. Mitochondr Physiol Network 2016-01-28, updated 2016-11-02.


OROBOROS (2016) MiPNet

Abstract: ROX.jpg Residual oxygen consumption (ROX) is sometimes referred to as 'non-mitochondrial respiration'. This may be correct to a large extent, but is not entirely accurate. In a preparation of purified isolated mitochondria, a small but significant ROX is observed after appropriate correction for instrumental background oxygen flux. In this case, ROX is 'mitochondrial non-ETS' rather than ‘non-mitochondrial’ respiration. In permeabilized and intact cells, ROX may be higher than in isolated mitochondria, and this increased part then would be the best measurement of non-mitochondrial respiration. Keilin (1926) introduced and accurately defined the term residual respiration.


O2k-Network Lab: AT Innsbruck Gnaiger E


Labels:




Coupling state: ETS"ETS" is not in the list (LEAK, ROUTINE, OXPHOS, ET) of allowed values for the "Coupling states" property. 

HRR: Theory 



Nomenclature

  • Previous editions (including Gnaiger 2014 MitoPathways): Mitochondrial respiration is frequently corrected for ROX, then distinguishing ROX-corrected ROUTINE, LEAK, OXPHOS or ETS (R, L, P and E) from the corresponding apparent fluxes that have not been corrected for ROX . Apparent fluxes (not corrected for ROX; R´, L´, P´ and E´) places the terminology into the conceptual context of physical chemistry (including kinetics), where e.g. apparent equilibrium constants, Keq´ (apparent Michaelis-Menten kinetic constants, Km´) are carefully distinguished from the less accessible (or inaccessible) 'true' constants, Keq (Km).
  • Mitochondrial physiology nomenclature: Despite the fact that the previously used nomenclature provides a conceptually consistent framework of physical chemistry, generalized applicability may gain from a shift to a pragmatic emphasis of the experimental context of mitochondrial physiology. ROX correction is a baseline correction, which may be evaluated by a direct measurement within an experimental assay, or by independent test experiments for critical evaluation of the best estimate for a particular ROX correction. The ROX correction, therefore, may be emphasized by labelling the ROX-corrected values as 'true' mitochondrial (mt) fluxes [R(mt), L(mt), P(mt) and E(mt)]. Unfortunately, the total R, L, P and E values in this mitochondrial physiology system carry opposite meanings to the physical chemistry system of terminology. Agreement is required for paving the way towards consistent data reporting and managing a meaningful database (but agreement is not even reached in hot debates on caloric units [J versus cal] or frozen debates on commonly used temperature scales [°C versus Faraday].


Keilin 1929: Residual respiration

'KCN, H2S and CO combine with some of the components of oxidase forming an inactive compound, with the result that cytochrome, or at least its components a’ and c’, as well as paraphenylenediamine added to the cells, are not oxidised. The respiratory process can be still carried out through the medium of some autoxidisable carriers such as haemochromogens, haematins, the component b’ of cytochrome, or some as yet unknown autoxidisable substances. This residual respiration, according to the nature of the cell, may represent a larger or smaller fraction of the total respiration of the cell.'
Keilin D (1929) Cytochrome and respiratory enzymes. Proc R Soc London Ser B 104:206-52.


Experimental tests on ROX

Is the preparation fully permeabilized?

ROX may be estimated in mitochondrial preparations in SUIT protocols which start at a respiratory state without added CHO substrates and without inhibitors, such that continuation of the SUIT protocol is possible for OXPHOS analysis. Some critical questions arise for evaluation, if this respiratory 'ROX state' represents a valid condition for estimation of ROX, and for comparison with ROX measured at the end of a SUIT protocol after titration of substrates and inhibitors of key elements of the electron transfer system (e.g. Rot, Mna and Ama as inhibitors of CI, CII and CIII). For evaluation of such an initial estimate of ROX, the following considerations are suggested.
  1. A preparation of permeabilized tissue or cells, Ptic, may contain a fraction of intact, non-permeabilized cells. Non-permeabilized cells have ROUTINE respiration that
    1. is higher than ROX;
    2. is not stimulated by addition of ADP;
    3. is not diminished over prolonged periods of time due to the presence of cellular endogenous substrates;
    4. can be stimulated by uncoupler titration;
    5. can be inhibited by Rot (CI) and Ama (CII), etc.
  2. Respiration of permeabilized tissue or cells incubated in a medium with significant concentrations of mitochondrial substrates
    1. is higher than ROX;
    2. is stimulated by addition of ADP (compare 1.2);
    3. is not diminished over prolonged periods of time due to the presence of exogenous substrates in the medium;
    4. can be stimulated by uncoupler titration,
    5. can be inhibited by Rot (CI) and Ama (CII), etc.
  3. In contrast, the acutal level of ROX of fully permeabilized cells responds to such tests as
    1. ROX is obtained after gradual depletion of mitochondrial internal substrates (gradual decline of oxygen consumption);
    2. ADP or uncoupler titrations accelerate this decline;
    3. Rot and Ama do not inhibit ROX;
    4. uncoupler titration does not stimulate ROX.


Related terms in Bioblast

OXPHOS-coupled energy cycles. Source: The blue book
P.jpg OXPHOS, P
R.jpg ROUTINE, R
E.jpg ETS, E
L.jpg LEAK, L
ROX.jpg ROX, R


List of publications: ROX