Template:SUIT-003

Steps and respiratory states

Step	State	Pathway	Q-junction	Comment - Events (E) and Marks (M) ROUTINE respiration in the physiological coupling state R. Externally added permeable substrates could contribute to this respiratory state.
ce2Omy	L			ce1;ce2Omy
ce3U	E			ce1;ce2Omy;ce3U 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. Noncoupled electron transfer state, ET state, with ET capacity E.
ce4Rot	ROX			ce1;ce2Omy;ce3U;ce4Rot Succinate pathway control state (S-pathway) after inhibiting CI with rotenone, which also inhibits the F-pathway. Rox is the residual oxygen consumption in the ROX state, due to oxidative side reactions, estimated either after inhibition of CIII (e.g. antimycin A, myxothiazol), CIV (e.g. Cyanide) or in the absence of endogenous fuel-substrates. Rox is subtracted from oxygen flux as a baseline for all respiratory states, to obtain mitochondrial respiration.

Step	State	Pathway	Q-junction	Comment - Events (E) and Marks (M)
ce5S				ce1;ce2Omy;ce3U;ce4Rot;ce5S Succinate, S ( type S-pathway to Q).
1Dig*	SE	S	CII	ce1;ce2Omy;ce3U;ce4Rot;ce5S;1Dig Multiple Digitonin titrations for complete plasma membrane permeabilization.
1c	SE	S	CII	ce1;ce2Omy;ce3U;ce4Rot;ce5S;1Dig;1U;1c 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]). Noncoupled electron transfer state, ET state, with ET capacity E.
2Ama	ROX			ce1;ce2Omy;ce3U;ce4Rot;ce5S;1Dig;1U;1c;2Ama 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). Rox is the residual oxygen consumption in the ROX state, due to oxidative side reactions, estimated either after inhibition of CIII (e.g. antimycin A, myxothiazol), CIV (e.g. Cyanide) or in the absence of endogenous fuel-substrates. Rox is subtracted from oxygen flux as a baseline for all respiratory states, to obtain mitochondrial respiration.

Step	Respiratory state	Pathway control	ET-Complex	Comment
## AsTm	AsTmE	CIV	CIV
## Azd	CHB

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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