Difference between revisions of "Q-redox state"

Latest revision as of 11:49, 10 March 2022

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Q-redox state

Description

The Q-redox state reflects the redox status of the Q-junction in the mitochondrial or chloroplast electron transfer system (ETS). Coenzyme Q (CoQ or Q, ubiquinone) is a mobile redox component located centrally in the mitochondrial ETS, while plastoquinones are essential mobile components in the photosynthetic system with a similar function. The Q-redox state depends on the balance between reducing capacities of convergent electron entries from fuel substrates into the Q-junction and oxidative capacities downstream of Q to the electron acceptor oxygen. Therefore, deficiencies in the mitochondrial ETS, originating from e.g. the malfunction of respiratory Complexes, can be detected by measuring the changes of the Q-redox state with respect to the respiratory activity.

A three-electrode system was implemented into the NextGen-O2k to monitor the Q-redox state continuously and simultaneously with respiratory oxygen consumption. Added CoQ2 reflects the mitochondrial Q-redox state when equilibrating both with the detecting electrode and the biological sites (e.g. Complexes I, II and III).

Communicated by Komlodi T, Cardoso LHD (last update 2021-02-09)

Calculation of the Q-redox fractions

The Q-redox state is expressed as the fraction of reduced Q (Q_r) in each steady state of a SUIT protocol. In order to calculate the reduced Q fraction, the raw Q signal (U_raw) is calibrated against the fully oxidized Q signal (U_ox) and the fully reduced Q signal (U_red). U_ox is measured in the presence of CoQ2 and isolated mitochondria. The CI inhibitor rotenone might have to be added to inhibit respiration of endogenous substrates. U_red is determined under anoxia after the sample consumed the accessible O₂ in the O2k-chamber. Q_r is calculated as a proportion of the fully reduced Q. The sum of the oxidized and reduced fractions of Q equals 1, Q_r+Q_ox = 1. In this formalism the intermediate redox state of semiquinone is not taken into account.

Further details: Komlodi 2021 BEC Q

Keywords

Bioblast links: Q - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>

Coenzyme Q

» Coenzyme Q

» Quinone, Ubiquinone Q; oxidized

» Quinol, Ubiquinol QH₂; reduced

» Semiquinone

» Coenzyme Q2

» Q-redox state

» Q-pools

Mitochondrial pathways, respiratory Complexes, and Q

» Q-cycle

» Q-junction

» Convergent electron flow

» NS-pathway

» FNS

» FNSGp

» N-pathway

» Reverse electron flow from CII to CI

» CI

» Rotenone

» Amytal

» Piericidin

» S-pathway

» CII

» Malonate

» F-pathway

» CETF, Electron-transferring flavoprotein complex

» Gp-pathway

» CGpDH, Glycerophosphate dehydrogenase complex

» CIII

» Myxothiazol

» Choline dehydrogenase

» Dihydro-orotate dehydrogenase

NextGen-O2k and Q-Module

» NextGen-O2k

» Q-Module

» Q-Sensor

» Cyclic voltammetry

» Three-electrode system

General

» Categories of SUIT protocols

» Electron transfer pathway

» Electron-transfer-pathway state

» F-junction

» N-junction

The Q-Module is part of the NextGen-O2k project

The Q-Module allows for monitoring of the redox state of electron transfer-reactive coenzyme Q at the Q-junction using the specific Q-Stoppers with the integrated three-electrode system and the modified electronics of the NextGen-O2k. Cyclic voltammetry is used for quality control and for defining the polarization voltage applied during Q-redox measurements.

Reference:

Komlódi T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2021) Coupling and pathway control of coenzyme Q redox state and respiration in isolated mitochondria. Bioenerg Commun 2021.3. https://doi.org/10.26124/bec:2021-0003

@@ Line 1: / Line 1: @@
 {{MitoPedia
-|abbr=Q<sub>r</sub>/Q<sub>t</sub>
+|abbr=
-|description= The '''Q redox state''' reflects the redox status of the [[Q-junction]] in the mitochondrial or chloroplast [[ETS|electron transfer system (ETS)]]. Ubiquinones, also known as [[Coenzyme Q |coenzyme Q]], and plastoquinones are essential mobile components of the mitochondria and chloroplasts that transfer electrons between the respiratory or photosynthetic complexes of the [[ETS]]. The Q redox state is dependent on the relative activities of the [[ETS]] enzymes that reduce and oxidize the quinones. Therefore, deficiencies in the mitochondrial [[ETS]], originating from ''e.g.'' the malfunction of respiratory enzymes (complexes), can be detected by measuring the changes of the Q redox state with respect to respiratory activity.
+|description= The '''Q-redox state''' reflects the redox status of the [[Q-junction]] in the mitochondrial or chloroplast [[ETS|electron transfer system (ETS)]]. [[Coenzyme Q]] (CoQ or Q, [[ubiquinone]]) is a mobile redox component located centrally in the mitochondrial [[ETS]], while plastoquinones are essential mobile components in the photosynthetic system with a similar function. The Q-redox state depends on the balance between reducing capacities of convergent electron entries from fuel substrates into the Q-junction and oxidative capacities downstream of Q to the electron acceptor oxygen. Therefore, deficiencies in the mitochondrial [[ETS]], originating from e.g. the malfunction of respiratory Complexes, can be detected by measuring the changes of the Q-redox state with respect to the respiratory activity.
+A three-electrode system was implemented into the NextGen-O2k to monitor the Q-redox state continuously and simultaneously with respiratory oxygen consumption. Added CoQ2 reflects the mitochondrial Q-redox state when equilibrating both with the detecting electrode and the biological sites (e.g. Complexes I, II and III).
 }}
+__TOC__
+ Communicated by [[Komlodi T]], [[Cardoso LHD]] (last update 2021-02-09)
+== Calculation of the Q-redox fractions ==
+:::: The Q-redox state is expressed as the fraction of reduced Q (Q<sub>r</sub>) in each steady state of a SUIT protocol.  In order to calculate the reduced Q fraction, the raw Q signal (''U''<sub>raw)</sub> is calibrated against the fully oxidized Q signal (''U''<sub>ox</sub>) and the fully reduced Q signal (''U''<sub>red</sub>). ''U''<sub>ox</sub> is measured in the presence of CoQ2 and isolated mitochondria. The CI inhibitor rotenone might have to be added to inhibit respiration of endogenous substrates. ''U''<sub>red</sub> is determined under anoxia after the sample consumed the accessible O<sub>2</sub> in the O2k-chamber. ''Q''<sub>r</sub> is calculated as a proportion of the fully reduced Q. The sum of the oxidized and reduced fractions of Q equals 1, ''Q''<sub>r</sub>+''Q''<sub>ox</sub> = 1. In this formalism the intermediate redox state of semiquinone is not taken into account.
-== Calculation of the Q redox ratios ==
+:::: Further details: [[Komlodi 2021 BEC Q]]
-To analyze the Q redox state, [[SUIT]] protocols are designed with one step in which the [[Q]] is fully reduced and one in which it is fully oxidized. The values obtained will be used to calculate the Q redox ratios.
-First, the signal is corrected for the fully oxidized Q state (Q<sub>ox</sub>), which can be measured, ''e.g.'' in the presence of [[Isolated mitochondria |isolated mitochondria]] and CoQ2. (To fully oxidize the Q-pool rotenone can be added which inhibits respiration of endogenous substrates. However, it cannot be applied when NADH- or F-linked O<sub>2</sub> flux is measured). Q<sub>ox</sub> is then subtracted from the raw Q signal for every step before the calculation of the ratios:
+== Keywords ==
-::: Q<sub>r</sub> = Q<sub>raw</sub>-Q<sub>ox</sub>
+{{Template:Keywords: Q}}
-Then, the Q redox ratio is calculated between the given Q-signal in the presence of different substrates/inhibitors/uncouplers (Q<sub>r</sub>) and the fully reduced Q state (Q<sub>t</sub>, also corrected for Q<sub>ox</sub>), which can be detected under anoxia for isolated mitochondria:
-::: Q<sub>r</sub>/Q<sub>t</sub>
-== The [[Q-Module]] is part of the [[NextGen-O2k]] project==
+== The [[Q-Module]] is part of the [[NextGen-O2k]] project ==
-{{Template:Q-Module}}
+:::: {{Template:Q-Module}}
- Communicated by [[Komlodi T]], [[Cardoso LHD]] 2020-07-28
 {{NextGen-O2k H2020-support}}
-{{Template:Keywords: Q}}