INVOLVEMENT OF THE PROTEASOME AND ANTIZYME IN ORNITHINE DECARBOXYLASEDEGRADATION BY A RETICULOCYTE LYSATE

Ornithine decarboxylase (ODC) degradation in a freshly prepared reticu locyte lysate was examined. Immunodepletion of proteasomes from the re ticulocyte lysate resulted in almost complete loss of ODC degradation. In contrast with the previously reported degradation in extracts of h epatoma tissue-culture (HTC) and Chinese-hamster ovary (CHO) cells or that by the purified 26 S proteasome, efficient degradation of ODC was observed in the lysate without exogenous antizyme, an ODC protein inh ibitor induced by polyamines, owing to the presence of a significant a mount of antizyme in the lysate. The degradation of ODC in the lysate was strongly suppressed on inactivation of antizyme in the lysate with antizyme inhibitor, a protein which binds to the antizyme and release s ODC from the ODC-antizyme complex. Thus the main pathway for ODC deg radation in a reticulocyte lysate was essentially the same as that cha racterized previously in extracts of HTC and CHO cells, namely an ATP- and antizyme-dependent 26 S proteasome-catalysed pathway that is pres umed to be responsible for ODC degradation in whole cells.