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Phosphorylation pathway

From Bioblast


high-resolution terminology - matching measurements at high-resolution


Phosphorylation pathway

Description

From Gnaiger 2014 MitoPathways

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 adenylate 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 ETS-competent substrate 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.