AbstractBy immunization of rabbits with discelectrophoretically purified rubredoxin‐reductase fromAc. calcoaceticusan antiserum against this enzyme was prepared. The antiserum was monospecifical to a diaphoretic activity, which had a RF‐value identical with the rubredoxin‐reductase‐RFvalue.It has been shown by discelectrophoresis, immunoelectrophoresis, OUCHTERLONY technique and kinetic investigations that crude extracts of bacteria grown on C16, malate, succinate or acetate contain rubredoxin‐reductase.By the LAURELL technique we demonstrated that the amount of the enzyme is nearly independent of the carbon source. There are only differences during the different grow