Destroys superoxide anion radicals which are normally produced within the cells and which are toxic to biological systems. 2 H(+) + 2 superoxide = H2O2 + O2 Binds 1 Fe cation per subunit. Homodimer. Strongly expressed in the stems of the young seedlings, etiolated seedlings and embryogenic calli, but only minimally expressed in the leaves and the roots. By light. Belongs to the iron/manganese superoxide dismutase family.