A POLAROGRAPHIC STUDY OF THE CATALYTIC MECHANISM OF THE IRON-CONTAINING SUPEROXIDE-DISMUTASE FROM ESCHERICHIA-COLI

The dependence of the activity of iron-containing superoxide dismutase from Escherichia coil on pH and ionic strength was investigated exten sively in the ranges 7.7-11.0 and 0.02-0.25 M respectively. The result s show that the enzymatic activity diminishes with both increasing pH and increasing ionic strength, reaching a minimum value at about pH 11 . The activity decrease with increasing pH was ascribed to a gradual t itration, by OH- ion, of the acid group Fe3+-H2O. This gives rise to a deprotonated enzymatic form with a residual activity which is about 1 0% that of the protonated form. The dependence of the activity on ioni c strength was interpreted as a Debye-Huckel effect.