Purification and properties of superoxide dismutase from Drosophila melanogaster

The major superoxide dismutase ("slow" electromorph) of the fruit fly, Drosophila melanogaster, has been purified to homogeneity. This enzyme contains 2 Cu2+ and 2 Zn2+/molecule. The ultraviolet absorption spectrum indicates a lack of tryptophan. This enzyme has a molecular weight of 32,000 and is composed of two subunits of equal size, which are joined by noncovalent interactions. Cyanide at 1 and 3 mM inhibits the activity of superoxide dismutase 92 and 100%, but 5 and 10 mM azide caused 15 and 30% inhibition. The isoelectric point, assessed by isoelectric focusing, is 5.3. Amino acid analyses, as well as the spectral and catalytic properties, are reported. The D. melanogaster superoxide dismutase does not cross-react with antibodies to bovine erythrocyte Cu-Zn-containing superoxide dismutase nor to Escherichia coli manganese- and iron-containing superoxide dismutases.