Complex II ambiguities

high-resolution terminology - matching measurements at high-resolution

Complex II ambiguities

Description

The Succinate pathway is represented in the literature in some cases with a surprising error which warrants an analysis of Complex II ambiguities. For clarification: "The substrate of CII is succinate, which is oxidized forming fumarate while reducing flavin adenine dinucleotide FAD to FADH2, with further electron transfer to the quinone pool. Whereas reduced NADH is a substrate of Complex I linked to dehydrogenases of the TCA cycle and mt-matrix upstream of CI, reduced FADH2 is a product of Complex II with downstream electron flow from CII to Q" (quote from Gnaiger 2020).

Abbreviation: CII ambiguities

Reference: Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002

FADH₂ and S-pathway

• FADH₂ appears in several publications as the substrate of CII in the forward direction of the Krebs cycle. This commonly found error requires correction. For clarification, see page 48 in Gnaiger (2020).

• Arnold 2022 J Biol Chem
• Martinez-Reyes 2020 Nat Commun
• Yepez 2018 PLOS One
• DeBerardinis 2016 Sci Adv
• Sanchez 2001 Br J Pharmacol

CII and fatty acid oxidation

"Since mitochondrial Complex II also participates in the oxidation of fatty acids (6), .." (quote from [ Lemmi et al 1990]).

• Ref 6: Tzagoloff A (1982) Mitochondria. Plenum, New York.

MitoPedia concepts: MiP concept 

MitoPedia topics: Enzyme, Substrate and metabolite