O2tolerant

O2tolerant refers to the ability of an organism or enzyme to function in the presence of oxygen. Many biological processes evolved in an oxygen-depleted environment, and the introduction of oxygen into Earth's atmosphere, known as the Great Oxidation Event, posed a significant challenge. Organisms that could not tolerate oxygen often died out or were restricted to anaerobic niches. In contrast, organisms that developed mechanisms to cope with or even utilize oxygen survived and diversified.

The toxicity of oxygen arises from its reactivity, particularly the formation of reactive oxygen species (ROS) such as superoxide radicals and hydrogen peroxide. These molecules can damage cellular components like DNA, proteins, and lipids. O2tolerant organisms possess various defense mechanisms against ROS, including antioxidant enzymes like superoxide dismutase and catalase, as well as non-enzymatic antioxidants such as vitamin E and glutathione.

In molecular biology and biochemistry, O2tolerant enzymes are those that retain their catalytic activity in the presence of oxygen. Many enzymes that evolved before the Great Oxidation Event are oxygen-sensitive and lose their function or are irreversibly damaged by oxygen. However, some enzymes, particularly those involved in aerobic respiration, have evolved to utilize oxygen or are inherently resistant to its damaging effects. Understanding O2tolerance is crucial for various fields, including astrobiology, evolutionary biology, and the development of industrial biocatalysts.