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. Retains over 90% of its activity between pH 5.6 and 7.0. Retains 85% of its activity at pH 4.0 and 60% of its activity at pH 12.0. Full activity is retained between 25 and 45 degrees Celsius. Homodimer. Belongs to the Cu-Zn superoxide dismutase family.