Fig. 9.

Mechanisms of H₂O₂ signaling. In the direct signaling pathway, H₂O₂ reacts directly with a redox switch. In the redox relay mechanism, the sensor of H₂O₂, a high-reactive protein such as a peroxiredoxin, relays the oxidation to a redox switch. The redox relay mechanism can be made more complex by the intervention of additional intermediates, as exemplified in the thioredoxin-peroxiredoxin model in which the protein responsible for the reduction of the redox sensor acts as a redox relay.