Template:SUIT-029 O2 mt D066

Steps and respiratory states

Step	State	Pathway	Q-junction	Comment - Events (E) and Marks (M)
1PM	PM_L(n)	N	CI	1PM NADH-linked substrates (type N-pathway to Q). Non-phosphorylating resting state (LEAK state); LEAK respiration L(n) in the absence of ADP, ATP, AMP (no adenylates).
2T	PM_L or PM_P	N	CI	1PM;2T NADH-linked substrates (type N-pathway to Q). In the absence of ATPase activity, the LEAK state is maintained. However, if ATPases are active and thus generate ADP, respiration coupled to phosphorylation is stimulated. Stimulation is limited up to OXPHOS capacity; therefore, higher ATPase activities cannot be determined.
2D	PM_P	N	CI	1PM;2T;2D NADH-linked substrates (type N-pathway to Q). OXPHOS capacity P (with saturating [ADP]), active OXPHOS state.
2c	PMc_P	N	CI	1PM;2T;2D;2c NADH-linked substrates (type N-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]).
3Omy	PM_LOmy	N	CI	1PM;2D;2c;3Omy NADH-linked substrates (type N-pathway to Q). Non-phosphorylating resting state (LEAK state); LEAK-respiration, L(Omy), after blocking the ATP synthase with oligomycin.
4U	PM_E	N	CI	1PM;2T;2D;2c;3Omy;4U NADH-linked substrates (type N-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.
5G	PGM_E	N	CI	1PM;2T;2D;2c;3Omy;4U;5G NADH-linked substrates (type N-pathway to Q). Noncoupled electron transfer state, ET state, with ET capacity E.
6S	PGMS_E	NS	CI+CII	1PM;2T;2D;2c;3Omy;4U;5G;6S Respiratory stimulation by simultaneous action of type N substrates & succinate, with convergent electron flow in the NS-pathway for reconstitution of TCA cycle function. Noncoupled electron transfer state, ET state, with ET capacity E.
6U	PGMS_E	NS	CI+CII	1PM;2T;2D;2c;3Omy;4U;5G;6S;6U Respiratory stimulation by simultaneous action of type N substrates & succinate, with convergent electron flow in the NS-pathway for reconstitution of TCA cycle function. 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.
7Rot	S_E	S	CI	1PM;2T;2D;2c;3Omy;4U;5G;6S;6U;7Rot Succinate pathway control state (S-pathway) after inhibiting CI with rotenone, which also inhibits the F-pathway. Noncoupled electron transfer state, ET state, with ET capacity E.
8Ama	ROX			1PM;2T;2D;2c;3Omy;4U;5G;6S;6U;7Rot;8Ama 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).