Monoclonal antibody studies on the properties and regulation of murine ornithine decarboxylase antizymes.

Seven monoclonal antibodies were prepared against rat liver ornithine decarboxylase antizyme, a unique regulatory protein of the enzyme induced by its products. The monoclonal antibodies reacted with antizymes from all the rat and mouse tissues examined, indicating that these antizymes share similar structural features, though some size heterogeneity has been reported for rat antizymes. A sandwich enzyme immunoassay which could detect 0.1 ng of antizyme was developed using these antibodies. The amount of antizyme protein in rat liver, analyzed by the immunoassay, increased on putrescine treatment in parallel with antizyme activity, indicating that the changes in antizyme activity were attributable to the changes in the amount of its protein. The putrescine-induced increase of antizyme protein, as well as that of its activity, was completely inhibited by cycloheximide but not by actinomycin D, confirming the importance of post-transcriptional regulation in antizyme induction.