Life in an oxygen atmosphere poses many challenges for organisms. Obligate aerobes and aerotolerant organisms benefit from the use of oxygen as a terminal electron acceptor. Transfer of electrons from organic substrates to oxygen releases a large amount of energy, some of which is stored by the organisms as metabolically usable "high energy" compounds. The risks to these organisms, and particularly to obligate anaerobes, arise from the production of a small but significant quantity of partially reduced oxygen metabolites. The singly reduced metabolite, superoxide radical, reacts deleteriously with cell components, causing damage that can be lethal to the cell. Hydrogen peroxide, the two electron reduction product of oxygen, is a strong oxidant, especially if transition metal ions are present. Each metabolite reacts independently with cell components, but superoxide and hydrogen peroxide reacting in concert give rise to the strongly oxidizing hydroxyl radical.

Organisms that evolved to use oxygen also evolved the antioxidant enzymes, superoxide dismutase and catalase. The superoxide dismutases are a family of metalloproteins that scavenge the reactive superoxide radical. Catalases, typically heme-containing proteins, catalyze the disproportionation of hydrogen peroxide. Data are consistent with the cytoprotective roles for these enzyme systems. Some obligate anaerobes contain superoxide dismutase and are in turn more aerotolerant than anaerobes lacking the enzyme. Superoxide dismutase in anaerobes may have a role in establishing an infected lesion in animals and human beings.

Our objectives are to understand the structures-function relationships among superoxide dismutases in anaerobes and to determine the biological role of the enzyme in anaerobes. In addition, low molecular weight mimics of SOD activity are being explored. Techniques of enzymology, protein chemistry, anaerobic microbiology, and genetic technology are used to achieve these objectives.

Clark, E. A. and E. M. Gregory (2001) Is Porphyromonas asaccharolytica superoxide dismutase cambialistic? Virginia Journal of Science, 52(2):121.

Shirkey, B., Kovarcik, D.P., Wright, D.J., Wilmoth, G., Prickett, T.F., Helm, R.F., Gregory, E.M., and Potts. M.(2000) Active Fe-Containing Superoxide Dismutase and Abundant sodF mRNA in Nostoc commune (Cyanobacteria) after Years of Desiccation. J. Of Bacteriology. 182:189-197   [Abstract]

Shirkey, B., Kovarcik, D.-P., Wright, D. J., Wilmoth, G., Prickett, T. F., Helm, R. F., Gregory, E. M., Potts, M. (2000) Active Fe-Containing Superoxide Dismutase and Abundant sodF mRNA in Nostoc commune (Cyanobacteria) After Years of Desiccation. J. Bacteriol. 182(1):189-197.   [Abstract]

Liu, Z.-X., Robinson, G. B., and Gregory, E. M. (1994) Preparation and characterization of Mn-salophen complex with superoxide scavenging activity. Arch. Biochem. Biophys. 315: 74-81.   [Abstract]

Juan, J.-Y., Keeney, S. N., and Gregory, E. M. (1991) Reconstitution of the Deinococcus radiodurans aposuperoxide dismutase. Arch. Biochem. Biophys. 286: 257-263.   [Abstract]

Chen, Y. and Gregory, E. M. (1991) In vivo metal substitution in Bacteroides fragilis superoxide dismutase. Free Rad. Res. Commun. 12/13 (Proceedings) 313-318.

Barkley, K. B. and Gregory, E. M. (1990) Tetrameric manganese superoxide dismutases from anaerobic Actinomyces. Arch. Biochem. Biophys. 280: 192-200.   [Abstract]