Coenzyme Q 10 and related quinones oxidize H 2 S to polysulfides and thiosulfate.

In the canonical pathway for mitochondrial H ₂ S oxidation electrons are transferred from sulfide:quinone oxidoreductase (SQR) to complex III via ubiquinone (CoQ ₁₀ ). We previously observed that a number of quinones directly oxidize H ₂ S and we hypothesize that CoQ ₁₀ may have similar properties. Here we examine H ₂ S oxidation by CoQ ₁₀ and more hydrophilic, truncated forms, CoQ ₁ and CoQ ₀ , in buffer using H ₂ S and polysulfide fluorophores (AzMC and SSP4), silver nanoparticles to measure thiosulfate (H ₂ S ₂ O ₃ ), mass spectrometry to identify polysulfides and O ₂ -sensitive optodes to measure O ₂ consumption. We show that all three quinones concentration-dependently catalyze the oxidization of H ₂ S to polysulfides and thiosulfate in buffer with the potency CoQ ₀ >CoQ ₁ >CoQ ₁₀ and that CoQ ₀ specifically oxidizes H ₂ S to per-polysulfides, H ₂ S _2,3,4 . These reactions consume and require oxygen and are augmented by addition of SOD suggesting that the quinones, not superoxide, oxidize H ₂ S. Related quinones, MitoQ, menadione and idebenone, oxidize H ₂ S in similar reactions. Exogenous CoQ ₀ decreases cellular H ₂ S and increases polysulfides and thiosulfate production and this is also O ₂ -dependent, suggesting that the quinone has similar effects on sulfur metabolism in cells. Collectively, these results suggest an additional endogenous mechanism for H ₂ S metabolism and a potential therapeutic approach in H ₂ S-related metabolic disorders.
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