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Equilibration of adenylates in the mitochondrial intermembrane space maintains respiration and regulates cytosolic metabolism
- Source :
- Journal of Experimental Botany. 57:2133-2141
- Publication Year :
- 2006
- Publisher :
- Oxford University Press (OUP), 2006.
-
Abstract
- Adenylate kinase (AK) uses one each of Mg-complexed and free adenylates as substrates in both directions of its reaction. It is very active in the mitochondrial intermembrane space (IMS), but is absent from the mitochondrial matrix where low [ADP] upon intensive respiration limits the respiratory rate. AK activity in the IMS is linked to ATP/ADP exchange across the inner mitochondrial membrane by using ATP (imported from the matrix) and AMP as substrates, the latter provided by apyrase and other AMP-generating reactions. The ADP formed by AK is exported to the matrix (in exchange for ATP), providing a mechanism for regeneration of ADP during respiration. From the AK equilibrium, and taking pH values characteristic of subcellular compartments, [Mg2+] in the IMS is calculated as 0.4-0.5 mM and in the cytosol as 0.2-0.3 mM, whereas the MgATP:MgADP ratio in the IMS and cytosol is 6-9 and 10-15, respectively. These represent optimal conditions for transport of adenylates (via the maintenance of an ATPfree:ADPfree ratio close to 1) and mitochondrial respiratory rates (via the maintenance of submillimolar [ADPfree] in the IMS). This, in turn, has important consequences for mitochondrial and cytosolic metabolism, including regulation of the protein phosphorylation rate (via changes in the MgATP:AMPfree ratio) and allosteric regulation of mitochondrial and cytosolic enzymes. Metabolomic consequences are discussed in connection with the calculation of metabolic fluxes from subcompartmental distributions of total adenylates and Mg2+.
- Subjects :
- Adenine Nucleotides
Physiology
Apyrase
Mitochondrial intermembrane space
Adenylate Kinase
Cell Respiration
Adenylate kinase
Plant Science
Hydrogen-Ion Concentration
Plants
Mitochondrion
Biology
Mitochondria
Cytosol
Biochemistry
Mitochondrial matrix
Homeostasis
Magnesium
ATP–ADP translocase
Intermembrane space
Inner mitochondrial membrane
Subjects
Details
- ISSN :
- 14602431 and 00220957
- Volume :
- 57
- Database :
- OpenAIRE
- Journal :
- Journal of Experimental Botany
- Accession number :
- edsair.doi.dedup.....42684f10c39118fbcc7a3fa3a243304c