Editing Superoxide dismutase (section)

=== Selective Pressure and Enzyme Evolution ===
The atmospheric accumulation of highly reactive O<sub>2</sub> likely exercised a strong selective pressure against anaerobic organisms, and led to the adaptive evolution of oxygen utilization in metabolism (Boden ''et al''. 2021).<ref>Boden ''et al''. (2021). Timing the evolution of antioxidant enzymes in cyanobacteria. ''Nat Commun 12'', 4742. <nowiki>https://doi.org/10.1038/s41467-021-24396-y</nowiki>.</ref> The process of [[oxidative phosphorylation]] and aerobic respiration permitted a 400-fold increase in energy extraction efficiency per mole glucose as compared to anaerobic respiration. Although the increased yield of [[Adenosine triphosphate|adenosine triphosphate (ATP)]], a common form of cellular energy currency, was metabolically beneficial, the tradeoff between efficiency and risk to the metabolic machinery grew more prominent. Behaving as the terminal [[electron acceptor]] during [[cellular respiration]], the high rate of O<sub>2</sub> electron flux is accompanied by an increased risk of ROS formation, which can induce irreversible damage to cellular organelles and their processes (Case 2017).<ref>Case (2017). On the Origin of Superoxide Dismutase: An Evolutionary Perspective of Superoxide-Mediated Redox Signaling. ''Antioxidants,'' ''6''(4): 82. doi.org/10.3390/antiox6040082.</ref> In response to the accumulation of the hazardous metabolic byproducts of aerobic respiration, biological systems evolved various strategies to counteract [[Oxygen toxicity|O<sub>2</sub> toxicity.]]