Functional differences between manganese and iron superoxide dismutases in Escherichia coli K-12

• Published in: The Journal of biological chemistry Vol. 267; no. 34; pp. 24253 - 24258
• Main Authors: HOPKIN, K. A, PAPAZIAN, M. A, STEINMAN, H. M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05-12-1992
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Drug Resistance, Microbial; Enzymes and enzyme inhibitors; Escherichia coli - drug effects; Escherichia coli - enzymology; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Glucosephosphate Dehydrogenase - metabolism; Hydro-Lyases - metabolism; Iron - metabolism; Isoenzymes - genetics; Isoenzymes - metabolism; Isopropyl Thiogalactoside - pharmacology; Kinetics; Manganese - metabolism; Oxidoreductases; Paraquat - pharmacology; Plasmids; Promoter Regions, Genetic; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; Enzymatic activity; Structure activity relation; Enzyme; Escherichia coli; Bacteria; Superoxide dismutase; Iron; Antioxidant; Biological activity; Enterobacteriaceae; Manganese
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)35758-2

Superoxide dismutases are enzymes that defend against oxidative stress through decomposition of superoxide radical. Escherichia
coli contains two highly homologous superoxide dismutases, one containing manganese (MnSOD) and the other iron (FeSOD). Although
E. coli Mn and FeSOD catalyze the dismutation of superoxide with comparable rate constants, it is not known if they are physiologically
equivalent in their protection of cellular targets from oxyradical damage. To address this issue, isogenic strains of E. coli
containing either Mn or FeSOD encoded on a plasmid and under the control of tac promoter were constructed. SOD specific activity
in the Mn and FeSOD strains could be controlled by the concentration of isopropyl beta-thiogalactoside in the medium. The
tolerance of these strains to oxidative stress was compared at equal Mn and FeSOD specific activities. Our results indicate
that E. coli Mn and FeSOD are not functionally equivalent. The MnSOD is more effective than FeSOD in preventing damage to
DNA, while the FeSOD appears to be more effective in protecting a cytoplasmic superoxide-sensitive enzyme. These data are
the first demonstration that Mn and FeSOD are adapted to different antioxidant roles in E. coli.