Introduction 02-is abundantly produced in aerobic organisms, and the superoxide
dismutases (SODs) appear ample for the task of scavenging 02-. The SODs maintain the
steady-state [02"-] at a remarkably low level of~ 10-1 M inside diverse cells and organelles.
1 This [O2"-] is roughly equivalent to 1 02"-molecule in 20 bacteria or 5000 molecules in a
much larger mammalian cell. These low, steady-state intracellular 02'-levels and high levels
of SOD expression are essential because of the extreme reactivity and toxicity of 02"-. 2, 3 1 …