Destroys radicals which are normally produced within the cells and which are toxic to biological systems. May confer survival advantage by accelerating dismutation of superoxide of environmental origin to hydrogen peroxide, disruptive to the normal mucociliary clearance process in the host. 2 H(+) + 2 superoxide = H2O2 + O2 Binds 1 copper ion per subunit. Binds 1 zinc ion per subunit. Homodimer. Belongs to the Cu-Zn superoxide dismutase family.