Figure 5.

Redox and phosphorylation post-translational modifications and the regulation of TCA cycle enzymes and ETC components. Phosphorylation is shown by circled P, and Trx-dependent reduction is depicted by triangles with R. Abbreviations of the mitochondrial matrix enzymes and ETC components: ACO, aconitase; AOX, alternative oxidase; I, II, III, IV, complexes I–IV; CS, citrate synthase; FUM, fumarase; GDC, glycine decarboxylase complex; ICDH, isocitrate dehydrogenase; IMM, inner mitochondrial membrane; IMS, intermembrane space; MDH, malate dehydrogenase; NDA, internal rotenone-insensitive NADH dehydrogenase; NDB1 and NDB2, external rotenone-insensitive NADPH and NADH dehydrogenases; NDC, internal rotenone-insensitive NADPH dehydrogenase; OGDH, 2-oxoglutarate dehydrogenase complex; PDC, pyruvate dehydrogenase complex; SCS, succinyl-CoA synthetase; SHMT, Ser hydroxymethyltransferase. Oxo-acids activating AOX isoforms are highlighted in green; citrate and isocitrate causing transcriptional activation of AOX and NDA are highlighted in blue. The biochemical reactions and electron transport are indicated by black thin lines with arrows, whereas H₂O formation is shown in brown color. The light blue arrows indicate the supply of redox equivalents to ETC, the dark blue arrows indicate nitric oxide (NO) production, and the red arrows show superoxide anion (O₂⁻) production. The figure was substantially modified from Møller et al. (2020a)