Immunological homology among azoreductases from Clostridium and Eubacterium strains isolated from human intestinal microflora.

Azoreductases from several anaerobic intestinal bacteria have been shown to reduce azo dyes to carcinogenic aromatic amines. To evaluate the structural similarities of azoreductases from four species of Clostridium and one species of Eubacterium, a polyclonal antibody against purified Clostridium perfringens azoreductase was generated in rabbits. This antibody inhibited the azoreductase activity of all five bacteria tested. ELISA showed different degrees of binding of the antibody to various species of bacteria. In a Western blot, the antibody reacted with the purified azoreductases from all four Clostridium species and the Eubacterium species. These results demonstrate that the azoreductases from the bacteria tested share similar antigenic domains, which are probably located in the active site of the enzyme. Azoreductases from these intestinal bacteria are similar enough to be considered as a single group of enzymes with respect to their functions and antigenicity.