Figure 3. Possible mechanisms for H₂O₂-dependent signal transduction.

(A) The redox relay mechanism uses a scavenging enzyme such as glutathione peroxidase (GPX) or peroxiredoxin (PRX) to transduce the H₂O₂ signal and oxidize the target protein. (B) With the floodgate model, H₂O₂ inactivates the scavenger, perhaps through hyperoxidation to sulfinic (SO₂⁻) acid or through a post-translational modification (PTM), to allow for H₂O₂-mediated oxidation of the target protein. (C) The scavenging enzymes accept H₂O₂ oxidation and transfer the oxidation to an intermediate redox protein such as thioredoxin (TRX), which subsequently oxidizes the target protein. (D) Dissociation of the target protein from the oxidized scavenging enzyme results in target protein activation.