Template:SUIT-019

Steps and respiratory states

Step	State	Pathway	Q-junction	Comment - Events (E) and Marks (M)
1PalM	PalML	F(N)	CETF	1PalM Respiratory stimulation of the FAO-pathway, F, by fatty acid FA in the presence of malate M. Malate is a type N substrate (N), required for the F-pathway. In the presence of anaplerotic pathways (e.g., mitochondrial malic enzyme, mtME) the F-pathway capacity is overestimated, if there is an added contribution of NADH-linked respiration, F(N) (see SUIT-002). The FA concentration has to be optimized to saturate the FAO-pathway, without inhibiting or uncoupling respiration. Non-phosphorylating resting state (LEAK state); LEAK respiration L(n) in the absence of ADP, ATP, AMP (no adenylates).
2D	PalMP	F(N)	CETF	1PalM;2D Respiratory stimulation of the FAO-pathway, F, by fatty acid FA in the presence of malate M. Malate is a type N substrate (N), required for the F-pathway. In the presence of anaplerotic pathways (e.g., mitochondrial malic enzyme, mtME) the F-pathway capacity is overestimated, if there is an added contribution of NADH-linked respiration, F(N) (see SUIT-002). The FA concentration has to be optimized to saturate the FAO-pathway, without inhibiting or uncoupling respiration. OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
2c	PalMP	F(N)	CETF	1PalM;2D;2c 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]). Respiratory stimulation of the FAO-pathway, F, by fatty acid FA in the presence of malate M. Malate is a type N substrate (N), required for the F-pathway. In the presence of anaplerotic pathways (e.g., mitochondrial malic enzyme, mtME) the F-pathway capacity is overestimated, if there is an added contribution of NADH-linked respiration, F(N) (see SUIT-002). The FA concentration has to be optimized to saturate the FAO-pathway, without inhibiting or uncoupling respiration. OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
3Oct	PalOctMP	F(N)	CETF	1PalM;2D;2c;3Oct Respiratory stimulation of the FAO-pathway, F, by fatty acid FA in the presence of malate M. Malate is a type N substrate (N), required for the F-pathway. In the presence of anaplerotic pathways (e.g., mitochondrial malic enzyme, mtME) the F-pathway capacity is overestimated, if there is an added contribution of NADH-linked respiration, F(N) (see SUIT-002). The FA concentration has to be optimized to saturate the FAO-pathway, without inhibiting or uncoupling respiration. OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
4P	PalOctPMP	FN	CETF&I	1PalM;2D;2c;3Oct;4P Respiratory stimulation of the FAO-pathway, F, by fatty acid, FA, in the presence of malate, M. Malate is a type N substrate (N), required for the F-pathway. The FA concentration has to be optimized to saturate the F-pathway, without inhibiting or uncoupling respiration. & NADH-linked substrates (type N-pathway to Q). Respiratory stimulation by simultaneous action of the F-pathway and N-pathway with convergent electron flow in the FN-pathway for evaluation of an additive or inhibitory effect of F. OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
5G	PalOctPGMP	FN	CETF&I	1PalM;2D;2c;3Oct;4P;5G Respiratory stimulation of the FAO-pathway, F, by fatty acid, FA, in the presence of malate, M. Malate is a type N substrate (N), required for the F-pathway. The FA concentration has to be optimized to saturate the F-pathway, without inhibiting or uncoupling respiration. & NADH-linked substrates (type N-pathway to Q). Respiratory stimulation by simultaneous action of the F-pathway and N-pathway with convergent electron flow in the FN-pathway for evaluation of an additive or inhibitory effect of F. OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
6U	PalOctPGME	FN	CETF&CI&II	1PalM;2D;2c;3Oct;4P;5G;6U Respiratory stimulation of the FAO-pathway, F, by fatty acid, FA, in the presence of malate, M. Malate is a type N substrate (N), required for the F-pathway. The FA concentration has to be optimized to saturate the F-pathway, without inhibiting or uncoupling respiration. & NADH-linked substrates (type N-pathway to Q). Respiratory stimulation by simultaneous action of the F-pathway and N-pathway with convergent electron flow in the FN-pathway for evaluation of an additive or inhibitory effect of F. 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.
7S	PalOctPGMSE	FNS	CI&CII	1PalM;2D;2c;3Oct;4P;5G;6U;7S Respiratory stimulation of the FAO-pathway, F, by fatty acid, FA, in the presence of malate, M. Malate is a type N substrate (N), required for the F-pathway. The FA concentration has to be optimized to saturate the F-pathway, without inhibiting or uncoupling respiration. & NADH-linked substrates (type N-pathway to Q). Respiratory stimulation by simultaneous action of the F-pathway and N-pathway with convergent electron flow in the FN-pathway for evaluation of an additive or inhibitory effect of F. Succinate, S ( type S-pathway to Q). Noncoupled electron transfer state, ET state, with ET capacity E.
8Rot	SE	S	CII	1PalM;2D;2c;3Oct;4P;5G;6U;7S;8Rot Succinate pathway control state (S-pathway) after inhibiting CI with rotenone, which also inhibits the F-pathway. Succinate, S ( type S-pathway to Q). Noncoupled electron transfer state, ET state, with ET capacity E.
9Ama	ROX			1PalM;2D;2c;3Oct;4P;5G;6U;7S;8Rot;9Ama 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).

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