Molecular and functional aspects of superoxide dismutases

Abstract

Superoxide dismutases are ubiquitously distributed in all biological systems including prokaryotic, eukaryotic and plant cells. These proteins contain either copper and zinc or manganese or iron in the active centre, respectively. During the catalytic activity, the superoxide anion is converted into dioxygen and hydrogen peroxide. Cu2Zn2 superoxide dismutase is one of the most intensively studied metalloproteins. The primary structure of many of these proteins has been elucidated. A convincing structure-function correlation was deduced from biophysical and chemical data. The influence of the protein backbone on the reactivity of the metal was thoroughly studied. Of special interest was the catalytic centre of Cu2Zn2 superoxide dismutase. The molecular architecture of the phylogenetically older iron and manganese enzymes is far less understood. At present, the clinical and biochemical aspects of reactive oxygen species enjoy a marked interest, as they are thought to be responsible for the oxygen derived cell-damage. This may reflect the overwhelming number of different assay systems described for the evaluation of superoxide dismutase activity. The most suitable and convenient assays are briefly discussed. The model chemistry for superoxide dismutases of low molecular mass complexes of transition metals is reviewed. Emphasis is placed on the biological significance of superoxide dismutase active copper ligands, frequently used as antiinflammatory drugs. The interaction of reactive oxygen species with superoxide dismutases and the biochemical and clinical relevance of this enzyme are critically summarized.