Free OXPHOS capacity

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Bioblasts - Richard Altmann and MiPArt by Odra Noel
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Free OXPHOS capacity


Free OXPHOS capacity The free OXPHOS capacity, ≈P, is the OXPHOS capacity corrected for LEAK respiration, ≈P = P-L. ≈P is the scope for ADP stimulation, the respiratory capacity potentially available for phosphorylation of ADP to ATP. Oxygen consumption in the OXPHOS state, therefore, is partitioned into the free OXPHOS capacity, ≈P, strictly coupled to phosphorylation, ~P, and nonphosphorylating LEAK respiration, LP, compensating for proton leaks, slip and cation cycling: P = ≈P+LP. It is frequently assumed that LEAK respiration, L, as measured in the LEAK state, overestimates the LEAK component of respiration, LP, as measured in the OXPHOS state, particularly if the protonmotive force is not adjusted to equivalent levels in L and LP. However, if the LEAK component increases with enzyme turnover during P, the low enzyme turnover during L may counteract the effect of the higher Δpmt.

Abbreviation: ≈P

Reference: Gnaiger 2020 MitoPathways

MitoPedia concepts: Respiratory state, Recommended 

MitoPedia topics: EAGLE 

Communicated by Gnaiger E 2014-08-09, edited 2015-01-19.

Coupling control states for ≈P

» Respiratory state

Flux control factor

» Flux control factor, FCF


Free ET capacity Free ET capacity, ≈E = E-L
netOXPHOS control ratio netOXPHOS control ratio, ≈P/E control ratio: ≈P/E = (P-L)/E
ET-coupling efficiency ET-coupling efficiency, E-L control factor: j≈E = ≈E/E = (E-L)/E = 1-L/E