The charge distribution and Fukui function in the superoxide dismutases were calculated in terms of an atom-bond electronegativity equalization method (ABEEM). The results show that charge transfers of metal ions range from 0.1e to 0.3e, and charge transfers of the coordinated atoms and others are quite small when the active center in the superoxide dismutase catalyzes the superoxide anion radical. Fukui function of a metal ion is bigger than those of the coordinated atoms and others at the active center, but smaller than those of the atoms in the inactive form combined with the inhibitors. The prediction that Mn, Fe and Cu ions are the active center sites in manganese-containing superoxide dismutase, iron-containing superoxide dismutase and copper- and zinc-containing superoxide dismutase, respectively, agrees with both the quantum chemical theoretical computation and the experiments.

Key words: atom-bond electronegativity equalization method, superoxide dismutase, charge distribution, Fukui function, reaction activity