The two faces of peroxiredoxins

https://commons.wikimedia.org/wiki/File:Janus_coin.png

by Larissa Anastácio da Costa Carvalho

In the antiquity, many cities protected their territories by surrounding fortifications, with giant gates and arches working as unique gateways. The Roman god Janus, known as the protector of entrances or new-beginnings, is represented by a head with two faces in opposite directions. The two faces of Janus symbolize the duality of nature. Well, nature itself is marked by dichotomy. What in nature cannot be good and bad at the same time? That is the origin of the term Janus effect.

A remarkable example of the Janus effect is the mustard gas (1,1-thiobis-2-chloroethane). Used as a chemical weapon during World War I, it causes serious inflammation of the

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Peroxide signaling through thiol switches: chemical and biological aspects.

by Luis E. S. Netto

It is now well accepted that oxidants and other redox intermediates are not only damaging compounds, but also act as signaling molecules. This is especially evident for hydrogen peroxide, whose generation and degradation are finely regulated through multiple enzymatic systems. Proteins whose activities are based on Cysteine (Cys) residues are frequently reported to be oxidized in various biological systems in conditions where hydrogen peroxide is also generated. As the most parsimonious hypothesis, these proteins are frequently assumed to be directly oxidized by hydrogen peroxide, although this is not always supported by chemical data.

For instance, Protein Tyrosine Phosphatases

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