title: Electrostatic facilitation of the reaction catalyzed by the manganese-containing and the iron-containing superoxide dismutases.
abstract: Both the iron-containing and the manganese-containing superoxide dismutases from Escherichia coli show diminished activity with increasing ionic strength, indicative of electrostatic facilitation of the catalyzed reaction. Since both enzymes bear a net negative charge at the assay pH, as does the substrate, this suggests a cationic locale in the active site region. Acetylation of the enzymes inverted their response to increasing ionic strength. It thus appears that lysine residues provide the observed electrostatic facilitation. A specific inhibition by large monovalent anions was observed with the iron-containing superoxide dismutase and was taken to indicate the presence of a cationic group, within a hydrophobic crevice, at the active site.
mesh_terms: D000107:Acetylation; D001665:Binding Sites; D002384:Catalysis; D004563:Electrochemistry; D004926:Escherichia coli / Q000201:enzymology; D007501:Iron / Q000302:isolation & purification*; D008345:Manganese / Q000302:isolation & purification*; D009994:Osmolar Concentration; D013482:Superoxide Dismutase / Q000378:metabolism*
chemical_list: D008345:Manganese; D007501:Iron; D013482:Superoxide Dismutase