An Iron-containing Superoxide Dismutase from Escherichia coli

Escherichia coli B contains two electrophoretically distinct superoxide dismutases, one of which was previously isolated and found to be a mangano-protein. We have now isolated the other superoxide dismutase present in this organism. It contains 1 atom of Fe3+ per molecule and exhibits spectral properties reminiscent of aconitase. Its molecular weight is 38,700 and it is composed of two subunits of equal size which are not covalently joined. The amino acid composition of this ferrisuperoxide dismutase is similar to that of the mangano-enzyme previously isolated from the same source.