BACTERIAL [CU,ZN]-SUPEROXIDE DISMUTASE - PHYLOGENETICALLY DISTINCT FROM THE EUKARYOTIC ENZYME, AND NOT SO RARE AFTER ALL

Copper- and zinc-containing superoxide dismutases ([Cu,Zn]-SODs) are g enerally considered almost exclusively eukaryotic enzymes, protecting the cytosol and extracellular compartments of higher organisms from da mage by oxygen free-radicals. The recent description of a few examples of bacterial forms of the enzyme, located in the periplasm of differe nt Gram-negative micro-organisms, prompted a re-evaluation of this gen eral perception. A PCR-based approach has been developed and used succ essfully to identify bacterial genes encoding [Cu,Zn]-SOD in a wide ra nge of important human and animal pathogens - members of the Haemophil us, Actinobacillus and Pasteurella (HAP) group, and Neisseria meningit idis. Comparison of [Cu,Zn]-SOD peptide sequences found in Haemophilus ducreyi, Actinobacillus pleuropneumoniae, Actinobacillus actinomycete mcomitans, Pasteurella multocida, and N, meningitidis with previously described bacterial proteins and examples of eukaryotic [Cu,Zn]-SOD ha s shown that the bacterial proteins constitute a distinct family appar ently widely separated in evolutionary terms from the eukaryotic examp les. The widespread occurrence of [Cu,Zn]-SOD in the periplasm of bact erial pathogens, appropriately located to dismute exogenously derived superoxide radical anions, suggests that this enzyme may play a role i n the interactive biology of organisms with their hosts and so contrib ute to their capacity to cause disease.