Q-junction

high-resolution terminology - matching measurements at high-resolution

Q-junction

Description

The Q-junction is a junction for convergent electron flow in the electron transfer system (ETS) from type N substrates and mt-matix dehydrogenases through Complex I (CI), from type F substrates and FA oxidation through electron-transferring flavoprotein complex (CETF), from succinate (S) through Complex II (CII), from glycoreophosphate (Gp) through glycerophosphate dehydrogenase complex (CGpDH), from choline through choline dehydrogenase, from dihydro-orotate through dihydro-orotate dehydrogenase, and other enzyme complexes into the Q-cycle (ubiquinol/ubiquinone), and further downstream to Complex III (CIII) and CIV. The concept of the Q-junction, with the N-junction and F-junction upstream, provides the rationale for defining pathway control states and categories of SUIT protocols.

Reference: Gnaiger 2009 Int J Biochem Cell Biol, Gnaiger 2014 MitoPathways

MitoPedia concepts: MiP concept, SUIT concept 

MitoPedia methods: Respirometry 

MitoPedia topics: Enzyme 

Contributed by Gnaiger E 2010-08-15; edited 2016-02-12, 2016-03-28.

Convergent NS-linked electron flow at the Q-junction, exerting an additive effect on flux, versus electron gaiting for separation of single N- and S-input pathways (upper panel: Gnaiger 2009; lower panel: Hatefi 1962 J Biol Chem-XLII). Modified Fig. 1.5 in Gnaiger 2014 MitoPathways.

More details: »Respiratory complexes - more than five

» O2k-Publications: Q-junction effect

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• Electron transfer system, ETS

Electron transfer system

Q-junction

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Pathway control state

• Coupling control state E

ETS capacity

Noncoupled respiration