Manganese: A Versatile Antioxident Element

The metalloprotein that we now know as superoxide dismutase (SOD) was originally isolated in 1939 on the basis of its blue-green color and named hemocuprein, a copper protein with antioxidant activity. The importance of the SOD enzymes is indicated by their near ubiquitous distribution in the natural world.

Now we know that SOD enzymes evolved independently at least three times and that each contains redox-active metal ions at its active sites. But there remains a major puzzle in the SOD story: the surprising observation that simple inorganic manganous ion, Mn2+, without any protein at all, can functionally replace SOD enzymes in living cells in certain organisms that lack SOD enzymes. This phenomenon seems to defy the statement that a highly evolved metalloprotein active site is required for high SOD activity. The present talk will discuss the possibility that manganese may have an antioxidant function in higher organisms that is independent of its role when bound in MnSOD.