Difference between revisions of "Phosphorylation pathway"
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== OXPHOS and substrate level phosphorylation == | == OXPHOS and substrate level phosphorylation == | ||
:::: [[OXPHOS capacity]], measured as oxygen flux in coupled, ADP- and Pi-saturated mitochondria in an [[ | :::: [[OXPHOS capacity]], measured as oxygen flux in coupled, ADP- and Pi-saturated mitochondria in an [[Electron transfer-pathway state]], may be limited by the phosphorylation system capacity. Mitochondria are the location of the chemiosmotic DT-system, but additionally carry out substrate-level phosphorylation in the TCA-cycle at the step of [[succinyl-CoA synthase]], phosphorylating GDP to GTP or ADP to ATP (taken together as DT). This step must be considered in the mtDT-phosphorylation system. If succinate is externally added to mt-preparations, succinyl-CoA synthase is not involved. However, if succinate is formed in the mt-matrix from 2-oxoglutarate (alpha-ketoglutarate), substrate-level phosphorylation at succinyl-CoA synthase must be accounted for in the interpretation of P/O (P/O<sub>2</sub>) ratios. |
Revision as of 08:58, 20 October 2017
Description
The phosphorylation system is the functional unit utilizing the protonmotive force to phosphorylate ADP (D) to ATP (T), and may be defined more specifically as the DT-phosphorylation system or DT-system. The DT-system consists of adenine nucleotide translocase, phosphate carrier, and ATP synthase. Mitochondrial adenylate kinase, mt-creatine kinase and mt-hexokinase constitute extended components of the DT-phosphorylation system, controlling local AMP and ADP concentrations and forming metabolic channels. Since substrate-level phosphorylation is involved in the TCA-cycle, the mtDT system includes succinyl-CoA synthase (GDP to GTP or ADP to ATP).
Abbreviation: DT
Reference: Gnaiger 2009 Int J Biochem Cell Biol
MitoPedia concepts:
MiP concept,
SUIT concept
MitoPedia topics:
Enzyme
Communicated by Gnaiger E 2010-08-15, edited 2016-08-26.
OXPHOS and substrate level phosphorylation
- OXPHOS capacity, measured as oxygen flux in coupled, ADP- and Pi-saturated mitochondria in an Electron transfer-pathway state, may be limited by the phosphorylation system capacity. Mitochondria are the location of the chemiosmotic DT-system, but additionally carry out substrate-level phosphorylation in the TCA-cycle at the step of succinyl-CoA synthase, phosphorylating GDP to GTP or ADP to ATP (taken together as DT). This step must be considered in the mtDT-phosphorylation system. If succinate is externally added to mt-preparations, succinyl-CoA synthase is not involved. However, if succinate is formed in the mt-matrix from 2-oxoglutarate (alpha-ketoglutarate), substrate-level phosphorylation at succinyl-CoA synthase must be accounted for in the interpretation of P/O (P/O2) ratios.