Destroys radicals which are normally produced within the cells and which are toxic to biological systems. 2 H(+) + 2 superoxide = H2O2 + O2 Binds 1 copper ion per subunit. Binds 1 zinc ion per subunit. Homodimer. By sulfhydryl-containing molecules such as glutathione, DDT, and cysteine. Belongs to the Cu-Zn superoxide dismutase family.