antioxidants Review Metabolic Targets of Coenzyme Q10 in Mitochondria Agustín Hidalgo-Gutiérrez 1,2,*, Pilar González-García 1,2, María Elena Díaz-Casado 1,2, Eliana Barriocanal-Casado 1,2, Sergio López-Herrador 1,2, Catarina M. Quinzii 3 and Luis C. López 1,2,* 1 Departamento de Fisiología, Facultad de Medicina, Universidad de Granada, 18016 Granada, Spain;
[email protected] (P.G.-G.);
[email protected] (M.E.D.-C.);
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[email protected] (S.L.-H.) 2 Centro de Investigación Biomédica, Instituto de Biotecnología, Universidad de Granada, 18016 Granada, Spain 3 Department of Neurology, Columbia University Medical Center, New York, NY 10032, USA;
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[email protected] (L.C.L.); Tel.: +34-958-241-000 (ext. 20197) (L.C.L.) Abstract: Coenzyme Q10 (CoQ10) is classically viewed as an important endogenous antioxidant and key component of the mitochondrial respiratory chain. For this second function, CoQ molecules seem to be dynamically segmented in a pool attached and engulfed by the super-complexes I + III, and a free pool available for complex II or any other mitochondrial enzyme that uses CoQ as a cofactor. This CoQ-free pool is, therefore, used by enzymes that link the mitochondrial respiratory chain to other pathways, such as the pyrimidine de novo biosynthesis, fatty acid β-oxidation and amino acid catabolism, glycine metabolism, proline, glyoxylate and arginine metabolism, and sulfide oxidation Citation: Hidalgo-Gutiérrez, A.; metabolism. Some of these mitochondrial pathways are also connected to metabolic pathways González-García, P.; Díaz-Casado, in other compartments of the cell and, consequently, CoQ could indirectly modulate metabolic M.E.; Barriocanal-Casado, E.; López-Herrador, S.; Quinzii, C.M.; pathways located outside the mitochondria.