Figure 8.

H₂O₂-dependent signaling. H₂O₂ regulates signaling pathways by oxidation of thiol groups on cysteines within proteins that show a low pK_a, allowing the cysteine thiol group to exist as a thiolate anion (S⁻). H₂O₂ readily oxidizes thiolate, yielding SO⁻. Under high concentrations of H₂O₂, SO⁻ can undergo further oxidation to generate SO₂⁻ and SO₃⁻. SO⁻ can undergo further modifications including intra- or intermolecular disulfide bonds and S-gluthathiolation. (Modified from Finkel 2011.)