Adenosine triphosphate is a nucleotid and functions as the major carrier of chemical energy in the cells. As it transfers its energy to other molecules, it looses its terminal phosphate group and becomes adenosine diphosphate (ADP).
Reference: MiPNet03.02 Chemicals-Media
MitoPedia topics: Substrate and metabolite
Application in HRR
- ATP may be titrated to mt-preparations in ET-pathway competent substrate states to quantify ATPase activity before addition of ADP (D). As ATP is hydrolysed to ADP, OXPHOS is activated by ADP and respiration increases accordingly. High-quality isolated mitochondria contain zero or very low ATPase activity, such that resipration in the absence and presence of ATP is identical.
- Intracellular ATP levels are in the mM range, but many respiratory studies of mt-preparations are carried out at zero or µM concentrations of ATP. ADP kinetics of isolated rat liver mitochondria reveals a K´m,D of 56 µM ADP in the presence of 2 mM ADP (Gnaiger 2001), which is higher than the frequently cited value of 15 to 20 µM ADP.
- ATP stabilizes mitochondrial function and is therefore used in preservation solutions BIOPS and MiP03 (MiPNet03.02 Chemicals-Media). This may provide a rationale to add mM concentrations of ATP in the LEAK state in the absence of ATPase activity (Gnaiger et al 2000). In permeabilized fibres with high ATPase activity, ATP might be added after stimulation of respiration by ADP in various SUIT protocols. Arguments against additions of ATP, however, need to be considered, e.g. additional side effects exerted on other sensors in O2k-MultiSensor applications (TPP+).
--Gnaiger Erich 14:20, 16 February 2014 (CET)
Sources of ATP
Adenosine 5'-triphosphate disodium salt hydrate, C10H14N5O13P3Na2* (H2O)x)
Sigma A 2383, 5 g, store at -20 °C; FWanhydrous basis = 551.1
Alternative source: Merck 1191-1GM (Calbiochem, Adenosine 5′-Triphosphate Disodium Salt; FW = 551.2; store at -20 °C).
Caution: Chemicals stored in the fridge or freezer should be allowed to reach room temperature before opening.
Preparation of 500 mM ATP stock solution
- 1) Weigh 551.1 mg of ATP (FWanhydrous basis = 551.1).
- 2) Add 1.2 ml H2O.
- 3) Neutralize with 5 M KOH (approx. 400 µl) - ATP dissolves after addition of KOH (this is Solution A).
- 4) Check pH and adjust to pH 7 if necessary.
- 5) Adjust final volume to 2 ml and divide into 0.2 ml portions.
- 6) Store frozen at -80 °C.
Preparation of 500 mM ATP stock solution with 3 mM free Mg2+
MgCl2 (Scharlau MA0036: MgCl2.6H2O, FW = 203.3)
- 1) Add 162.64 mg MgCl2 to Solution A. A white precipitate forms, which dissolves after 1-2 min of stirring on magnetic stirrer at room temperature.
- 2) Follow steps 4-6 of the above instructions.
- Comment: In some cases it was observed, that after defreezing of the 'ATP-Mg' a white precipitate forms again. If this is the case we recommend to prepare the 500 mM ATP stock solution and a MgCl2 solution (0.8 mol MgCl2 /mol ATP) seperately and perform a titration of both solutions in series.
O2k manual titrations
- Titration volume: 4-20 µl using a 25 µl syringe.
- Final conc. in 2 ml O2k-chamber: 1-5 mM.