structural:scholar_edition, linguistic:paraphrasing
MnSODs

SODs containing Fe (FeSOD), Mn (MnSOD), or may contain either (Fe/MnSOD) are believed to have been the earliest SOD isoforms among life on early earth. During this time, Fe and Mn would have been highly bioavailable. The differences between the oxidation and reduction potentials of each metal is thought to have been advantageous to organism survival, allowing them to exist in environments with varying O concentration and metal availability.