FIG. 2.

Hydrogen peroxide as a signaling molecule. Extracellular- and intracellular-derived hydrogen peroxide causes the reversible oxidation of specific cysteine residues on redox-sensitive target proteins. Previously identified targets include phosphatases, kinases, transcription factors, membrane channels, cytoskeletal proteins, and proteases. Depending on the extent and duration of hydrogen peroxide exposure, the outcome for the affected cell can range from increased proliferation to cell death.