Biological Strategies Against Oxygen Toxicity Antioxidants, Etc

4 Biological Strategies Against Oxygen Toxicity Antioxidants, Etc. 

As expounded above, the rise of the oxygen content of the atmosphere starting around 2.2 billion years ago created a panic among the then-living organisms. Many of them did not survive. The rise was not abrapt, and hence the organisms had chances to evolve to develop the defense mechanisms against this toxicity. 

Of course, this may not be sufficient to counter the toxic effects of various types of oxygen-derived entities. Therefore, organisms have developed various means to destroy some very toxic oxygen entities, superoxide and hydroperoxide (and hydrogen peroxide). They have not developed very effective specific means to combat very reactive HO or RO radicals. 

In recent years, another group of enzymes has been discovered that quickly decomposes hydrogen peroxide. It is called peroxiredoxin and is found both in 

Hydroperoxides (ROOH) can be decomposed by enzymes called peroxidases. Most of peroxidases are dependent on iron as catalyst, but a few of them use manganese. A very interesting peroxidase, called glutathione peroxidase, uses selenium as its catalytic element. Selenium is one of the most toxic elements, but a very small quantity of it is required by almost all organisms. It is used for glutathione peroxide as well as a few other enzymes. This enzyme is much more efficient in destroying certain types of hydroperoxides than the other more common iron-dependent peroxidases. 

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