Copper/zinc superoxide dismutases in Dictyostelium discoideum: amino acid sequences and expression kinetics.

Genes for Copper/Zinc superoxide dismutases, designated sodA and sodB, in the cellular slime mold Dictyostelium discoideum were analyzed. It was found that these gene products contain charged amino acid residues and hydrophobic stretches in their N-terminal regions, suggesting that they are extracellular Cu/Zn superoxide dismutases. The sodA and sodB are expressed in cells in the growth phase and throughout the developmental phases, suggesting that they are the housekeeping genes. The sodA is induced by H(2)O(2) exposure but not by UV irradiation, whereas sodB is induced both by H(2)O(2) exposure and UV irradiation. Such distinct kinetics of the expression patterns suggests that these enzymes play unique roles in D. discoideum.