Figure 2. Molecular mechanisms of reactive oxygen species signaling.

ROS produced by a family of NADPH oxidase enzymes or by mitochondria (complexes I and III of the respiratory chain) are able to oxidize cysteine residues of several components of signaling pathways. This can cause an increase in ion-channel activity or activation of kinase activity. The most studied ROS signaling mechanism is the inhibition of phosphatase activity by H₂O₂, which in turn leads to kinase activation. ROS can also increase DNA binding to the transcription factor.

NOX: NADPH oxidase; ROS: Reactive oxygen species.