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.
Reference: Gnaiger 2020 MitoPathways
MitoPedia topics: EAGLE
Communicated by Gnaiger E 2014-08-09, edited 2015-01-19.
Coupling control states for ≈P
- Reference state, ZX: OXPHOS capacity, P = P´-ROX
- Background state, YX: LEAK respiration, L = L´-ROX
- Metabolic control variable, X=ZX-YX: Scope of ADP stimulation, free OXPHOS capacity, ≈P = P-L
Flux control factor
- » Flux control factor, FCF
- Coupling control factor, 1-YX/ZX: P-L coupling control factor, OXPHOS-coupling efficiency: j≈P = ≈P/P =(P-L)/P = 1-L/P
- Intact cells: Free ROUTINE activity, ≈R = R-L