Destroys superoxide anion radicals which are normally produced within the cells and which are toxic to biological systems (By similarity). Plays important role in chloroplast development, particularly in the maintenance of thylakoids membranes. Seems to act as a heterodimer with FSD3. 2 H(+) + 2 superoxide = H2O2 + O2 Binds 1 Fe cation per subunit. Activated by cpn20/cpn21 (in vitro). Heterodimer with FSD3 (PubMed:18996978). Interacts with MRL7 and PRDA1 (PubMed:24132784). By UV-B treatment. Induced by salt stress. Pale green phenotype. Abnormal plastids, highly vacuolated and without internal membrane structures like thylakoids. Belongs to the iron/manganese superoxide dismutase family.