State 3
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Whereas OXPHOS capacity is measured at saturating concentrations of ADP and Pi, State 3 is defined as ADP stimulated respiration in the presence of high ADP and Pi concentrations (Chance and Williams, 1955) which are not necessarily saturating. For instance, non-saturating ADP concentrations are applied in State 3 in pulse titrations to determine the P/O ratio in State 3โ4 (DโT) transitions, when saturating ADP concentrations would deplete the oxygen concentration in the closed oxygraph chamber before State 4 is obtained (Gnaiger et al 2000; Puchowicz et al 2004).
References
- Chance B, Williams GR (1955) Respiratory enzymes in oxidative phosphorylation. III. The steady state. J. Biol. Chem. 217: 409-427.
- Gnaiger E, Mรฉndez G, Hand SC (2000) High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc. Natl. Acad. Sci. USA 97: 11080-11085.
- Puchowicz MA, Varnes ME, Cohen BH, Friedman NR, Kerr DS, Hoppel CL (2004) Oxidative phosphorylation analysis: assessing the integrated functional activity of human skeletal muscle mitochondria โ case studies. Mitochondrion 4: 377-385.