Template:SUIT-006 O2 mt D022

Steps and respiratory states

Step	State	Pathway	Q-junction	Comment - Events (E) and Marks (M)
1SRot	SL	S	CII	1SRot Succinate, S ( type S-pathway to Q). Succinate pathway control state (S-pathway) after inhibiting CI with rotenone, which also inhibits the F-pathway. Non-phosphorylating resting state (LEAK state); LEAK respiration L(n) in the absence of ADP, ATP, AMP (no adenylates).
2D	SP	S	CII	1SRot;2D Succinate, S ( type S-pathway to Q). OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
2c	ScP	S	CII	1SRot;2D;2c Succinate, S ( type S-pathway to Q). OXPHOS capacity P (with saturating [ADP]), active OXPHOS state. Addition of cytochrome c yields a test for integrity of the mtOM (cytochrome c control efficiency). Stimulation by added cytochrome c would indicate an injury of the mtOM and limitation of respiration in the preceding state without added c due to loss of cytochrome c. Typically, cytochrome c is added immediately after the earliest ADP-activation step (OXPHOS capacity P with saturating [ADP]).
3(Omy)	PML(Omy)	N	CII	1SRot;2D;2c;3(Omy) Succinate, S ( type S-pathway to Q). Non-phosphorylating resting state (LEAK state); LEAK-respiration, L(Omy), after blocking the ATP synthase with oligomycin. The addition of oligomycin is optional depending on the experimental question to resolve. If it is known that Ln has the same values for LOmy for a kind of sample and substrates, this step may be skipped. If the carrier of oligomycin (EtOH) is used instead, it is possible to evaluate whether it affects respiration. In these cases, LEAK state is not reached again.
4U	SE	S	CII	1SRot;2D;2c;3(Omy);4U Succinate, S ( type S-pathway to Q). Uncoupler titration (avoiding inhibition by high uncoupler concentrations) to obtain electron transfer (ET) capacity E (noncoupled ET-state). Test for limitation of OXPHOS capacity P by the phosphorylation system (ANT, ATP synthase, phosphate transporter) relative to ET capacity E in mt-preparations: E-P control efficiency and E-L coupling efficiency. In living cells: E-R control efficiency and E-L coupling efficiency.
5Ama	ROX			1SRot;2D;2c;3(Omy);4U;5Ama Rox is the residual oxygen consumption in the ROX state, due to oxidative side reactions, estimated after addition of antimycin A (inhibitor of CIII). Rox is subtracted from oxygen flux as a baseline for all respiratory states, to obtain mitochondrial respiration (mt).

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Coupling control

» Coupling control state

» ET capacity

» OXPHOS capacity

» LEAK respiration

Pathway control

» Electron transfer pathway

» Fatty acid oxidation pathway control state, F

» NADH electron transfer-pathway state, N

» Succinate pathway control state, S

» NS-pathway control state, NS

» Glycerophosphate pathway control state, Gp

» Complex IV single step, CIV

» Anaplerotic pathway control state

Main fuel substrates

» Glutamate, G

» Glycerophosphate, Gp

» Malate, M

» Octanoylcarnitine, Oct

» Pyruvate, P

» Succinate, S

Glossary

» List of SUIT states

» SUIT concept