The article discusses the role of hydrogen peroxide as a signaling molecule in eukaryotic cells, highlighting its dual nature as both a cytotoxic agent and a regulator of various biological processes. Hydrogen peroxide is generated in response to various stimuli, including cytokines and growth factors, and plays a crucial role in regulating processes such as immune cell activation, vascular remodeling, and cell proliferation. The authors emphasize the importance of antioxidant enzymes in sensing and regulating hydrogen peroxide signaling, explaining how these enzymes act as sensors and regulators of signal transduction. They also explore the molecular mechanisms by which hydrogen peroxide is sensed, including the oxidation of cysteine residues in proteins and the interaction with Fe²⁺. The article further discusses the regulation of antioxidant enzyme activity, such as posttranslational modifications, and how these enzymes influence the cellular response to hydrogen peroxide. Finally, the authors conclude by emphasizing the need to consider multiple factors, including the site of hydrogen peroxide generation, antioxidant levels, and protein interactions, to fully understand hydrogen peroxide signaling.The article discusses the role of hydrogen peroxide as a signaling molecule in eukaryotic cells, highlighting its dual nature as both a cytotoxic agent and a regulator of various biological processes. Hydrogen peroxide is generated in response to various stimuli, including cytokines and growth factors, and plays a crucial role in regulating processes such as immune cell activation, vascular remodeling, and cell proliferation. The authors emphasize the importance of antioxidant enzymes in sensing and regulating hydrogen peroxide signaling, explaining how these enzymes act as sensors and regulators of signal transduction. They also explore the molecular mechanisms by which hydrogen peroxide is sensed, including the oxidation of cysteine residues in proteins and the interaction with Fe²⁺. The article further discusses the regulation of antioxidant enzyme activity, such as posttranslational modifications, and how these enzymes influence the cellular response to hydrogen peroxide. Finally, the authors conclude by emphasizing the need to consider multiple factors, including the site of hydrogen peroxide generation, antioxidant levels, and protein interactions, to fully understand hydrogen peroxide signaling.