The Q redox state reflects the redox status of the Q-junction in the mitochondrial or chloroplast electron transfer system (ETS). Ubiquinones, also known as 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.
Calculation of the Q redox ratios
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 (Qox), which can be measured, e.g. in the presence of 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 O2 flux is measured). Qox is then subtracted from the raw Q signal for every step before the calculation of the ratios:
- Qr = Qraw-Qox
Then, the Q redox ratio is calculated between the given Q-signal in the presence of different substrates/inhibitors/uncouplers (Qr) and the fully reduced Q state (Qt, also corrected for Qox), which can be detected under anoxia for isolated mitochondria:
The Q-Module is part of the NextGen-O2k project
In the NextGen-O2k project we are working on developing the Q-Module for the new series of our O2k-FluoRespirometer, the NextGen-O2k. The Q-Module allows us to monitor the Q redox state of the Q-junction using the specific Q-Stoppers with the integrated three-electrode system and the modified electronics inside the O2k housing.
Communicated by Komlodi T, Cardoso LHD 2020-07-28
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Mitochondrial pathways, respiratory Complexes, and Q
NextGen-O2k and Q-Module