Coenzyme Q₁₀ and related quinones oxidize H₂S to polysulfides and thiosulfate

In the canonical pathway for mitochondrial H₂S oxidation electrons are transferred from sulfide:quinone oxidoreductase (SQR) to complex III via ubiquinone (CoQ₁₀). We previously observed that a number of quinones directly oxidize H₂S and we hypothesize that CoQ₁₀ may have similar properties. Here we examine H₂S oxidation by CoQ₁₀ and more hydrophilic, truncated forms, CoQ₁ and CoQ₀, in buffer using H₂S and polysulfide fluorophores (AzMC and SSP4), silver nanoparticles to measure thiosulfate (H₂S₂O₃), mass spectrometry to identify polysulfides and O₂-sensitive optodes to measure O₂ consumption. We show that all three quinones concentration-dependently catalyze the oxidization of H₂S to polysulfides and thiosulfate in buffer with the potency CoQ₀>CoQ₁>CoQ₁₀ and that CoQ₀ specifically oxidizes H₂S to per-polysulfides, H₂S_2,3,4. These reactions consume and require oxygen and are augmented by addition of SOD suggesting that the quinones, not superoxide, oxidize H₂S. Related quinones, MitoQ, menadione and idebenone, oxidize H₂S in similar reactions. Exogenous CoQ₀ decreases cellular H₂S and increases polysulfides and thiosulfate production and this is also O₂-dependent, suggesting that the quinone has similar effects on sulfur metabolism in cells. Collectively, these results suggest an additional endogenous mechanism for H₂S metabolism and a potential therapeutic approach in H₂S-related metabolic disorders.