Quantitative biology of hydrogen peroxide signaling.

Hydrogen peroxide (H2 O2 ) controls signaling pathways in cells by oxidative modulation of the activity of redox sensitive proteins denominated redox switches. Here, quantitative biology concepts are applied to review how H2 O2 fulfills a key role in information transmission. Equations described lay the foundation of H2 O2 signaling, give new insights on H2 O2 signaling mechanisms, and help to learn new information from common redox signaling experiments. A key characteristic of H2 O2 signaling is that the ratio between reduction and oxidation of redox switches determines the range of H2 O2 concentrations to which they respond. Thus, a redox switch with low H2 O2 -dependent oxidability and slow reduction rate responds to the same range of H2 O2 concentrations as a redox switch with high H2 O2 -dependent oxidability, but that is rapidly reduced. Yet, in the first case the response time is slow while in the second case is rapid. H2 O2 sensing and transmission of information can be done directly or by complex mechanisms in which oxidation is relayed between proteins before oxidizing the final regulatory redox target. In spite of being a very simple molecule, H2 O2 has a key role in cellular signaling, with the reliability of the information transmitted depending on the inherent chemical reactivity of redox switches, on the presence of localized H2 O2 pools, and on the molecular recognition between redox switches and their partners.