Analysis of epitope regions for autoantibodies in catalase

Catalase is reported to be one of the target antigens for autoantibodies in various pathologies. To understand the mechanism of autoantibody production, we compared the several properties of autoantigenic epitopes (AE)-1 and -2 of mouse catalase, which reported to react with antibodies from sera of Helicobacter hepaticus-infected mice; AE-3 and -4 of rat catalase, which we found to be susceptible to autoimmunity; and antigenic epitope (E)-1 of H. pylori catalase, which is recognized by monoclonal antibodies produced by immunized mice. Amino acid sequences of AE-1 and -2 were similar among both mammalian and pathogenic microorganism catalases, whereas that of E-1 differed. Amino acid sequences of AE-3 and -4 were similar among mammalian catalases but differed from pathogenic microorganism catalases. Based on local relative rates of evolution, these vertebrate catalases were divided into 5 segments. E-1 included a faster evolving region, whereas AE-1 and -2 included a slowly evolving region; AE-3 and -4 comprised a slowly evolving patch within a faster evolving region. In conclusion, although AE-1 and -2 of catalase have been reported to contribute to autoimmune responses in animals infected with catalase-producing pathogens, AE-3 and -4 appear to have a different mechanism for autoantibody production.