Studies on the degradation of ornithine decarboxylase by the immunoblotting technique

The degradation of ornithine decarboxylase was studied by an immunoblotting technique. The immunoblots of mouse kidney and brain cytosol preparations revealed degradation fragments of unequal size. The immunoreactive fragments found in kidney cytosol corresponded to molecular weights of 46 kDa and 32 kDa, whereas 36 kDa fragment was dominant in brain cytosol. When kidney cytosol was exposed to microsomal fraction of mouse brain before analysis, the kidney enzyme was degraded to 36 kDa-fragment. The microsomal fraction of mouse kidney, in turn, when incubated with brain cytosol brought about the appearance of immunoreactive protein corresponding to molecular weight of 35 kDa that was also found in kidney preparation, which was incubated as homogenate before electrophoretic run and immunoblotting. These results show that microsomal fractions effectively degrade enzyme protein, and suggest that the regulation mechanisms by the in vivo degradation of the enzyme are dissimilar in these tissues.