Ornithine decarboxylase (EC 4.1.1.17) assay based upon the retention of putrescine by a strong cation-exchange paper

A simple and direct method for the detection of ornithine decarboxylase (EC 4.1.1.17) activity is presented. It is based upon the selective binding of putrescine to Whatman P81 paper, a strong cation-exchanger, in the presence of 0.1 m NH₃. The assay is easy to perform and has an advantage over the more frequently used CO₂ trapping methods which can yield spurious CO₂ formation due to the action of enzymes other than ornithine decarboxylase.