Talk:Succinate pathway

The succinate-linked respiration or S-pathway (succinate-induced respiratory state; previously used nomenclature: CII-linked respiration; SRot; see Gnaiger 2009 Int J Biochem Cell Biol) is achieved with succinate (S) as the single substrate, at ET-pathway-level 3. S supports electron flux through complex II (CII; see succinate dehydrogenase, SDH) to CII-bound flavin adenine dinucleotide (FADH₂) to the Q-junction. Inhibition of complex I (CI) by rotenone (Rot; or amytal, piericidine) prevents accumulation of oxaloacetate which is a potent inhibitor of SDH. After inhibition of CI by Rot, the NADH-linked dehydrogenases become inhibited by the redox shift from NAD⁺ to NADH. SDH is activated by S and ATP, which explains in part the time-dependent increase of respiration in isolated mitochondria after addition of Rot (first), S and ADP.

The S-pathway is induced in mt-preparations by addition of succinate&rotenone. In this case, only complex III and complex IV are involved in pumping protons from the matrix (positive phase) to the negative phase with a P/O ratio of 1.75 (P»/O₂ = 3.5).