The free ROUTINE activity, ≈R, is ROUTINE respiration corrected for LEAK respiration, ≈R = R-L. ≈R is the respiratory activity available for phosphorylation of ADP to ATP. Oxygen consumption in the ROUTINE state of respiration measured in intact cells, therefore, is partitioned into the free ROUTINE activity, ≈R, strictly coupled to phosphorylation, ~P, and nonphosphorylating LEAK respiration, LR, compensating for proton leaks, slip and cation cycling: R = ≈R+LR. It is frequently assumed that LEAK respiration, L, as measured in the LEAK state, overestimates the LEAK component of respiration, LR, as measured in the ROUTINE state, particularly if the protonmotive force is not adjusted to equivalent levels in L and LR. However, if the LEAK component increases with enzyme turnover during R, the low enzyme turnover during L may counteract the effect of the higher Δpmt.
Reference: Gnaiger 2014 MitoPathways
MitoPedia topics: EAGLE
Communicated by Gnaiger E 2014-09-21, edited 2015-01-19.