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Table 2 Respiratory states analyzed in the SUIT protocol designed for high-resolution respirometry assays

From: The disruption of mitochondrial axonal transport is an early event in neuroinflammation

Respiratory state Meaning
LEAK Respiration state uncoupled from ATP synthase activity, due to proton leakage and the circuit of electrons initiated after the addition of malate and glutamate in the absence of ADP
Complex I (CI) Respiration state of NADH-dependent complex I after the addition of ADP, in which the proton gradient of the intermembrane space is partially used by ATP synthase for oxidative phosphorylation (coupled respiration) and partially dissipated due to proton leakage (uncoupled respiration)
Complexes I and II (CI + CII) Measurement of FADH2-dependent complex II respiration together with complex I respiration after the addition of succinate
Uncoupling Endogenous respiration uncoupled from ATP synthesis through complex I and II substrates after the addition of oligomycin (ATP synthase inhibitor)
Electron transfer system capacity I + II (ETS I + II) Measurement of the electron transfer system’s maximum capacity through the non-physiological uncoupling of the internal mitochondrial membrane after the addition of FCCP (an ionophore or uncoupling agent that dissipates H+)
Electron transfer system capacity II (ETS II) Maximum respiration that only corresponds to complex II after the addition of rotenone (complex I inhibitor)
Complex IV (CIV) Respiration state of complex IV after complex III inhibition by antimycin A, and the addition of ascorbate and TMPD
  1. Explanation of all the mitochondrial respiratory states included in the SUIT protocol designed for high-resolution respirometry assays. The respiratory states were measured in a continuous manner (without breaks between enzymatic reactions), and in this way, the substrates from the first respiratory states are available for the following states