Structure and properties of copper-zinc superoxide dismutases

This chapter discusses structure and properties of copper–zinc superoxide dismutases. The superoxide radical anion is physiologically produced in controlled amounts in animals and plants from the one-electron reduction of dioxygen occurring in several metabolic pathways. Under pathological conditions, large amounts of superoxide and related active oxygen species are released. Thus, a twofold aspect of superoxide effects on living organisms emerges from the available experimental data. The actual role of superoxide dismutase enzymes in living organisms needs to be reconsidered in view of this wider framework. A natural monomeric species has been isolated from the periplasmic space of an Escherichia coli strain. This CuZnSOD displays a catalytic activity comparable to that of bovine SOD, but is highly sensitive to proteases. A comparison of sequences of different Cu2Zn2SODs shows that amino acids are invariant, and that most of them are residues close to or part of the active site.