Antizymes (AZs) are polyamine-induced proteins that promote degradation of ornithine decarboxylase (ODC), the key enzyme in the polyamine biosynthetic pathway []. AZs also negatively regulate polyamine transport into the cells through an unknown mechanism []. AZs are in turn regulated by antizyme inhibitors (AZIN1 and AZIN2), which are proteins homologous to ODC that bind to AZs and counteract their negative effect on ODC [].Antizyme inhibitor 2 (AZIN2) affects polyamine homeostasis not only by increasing ODC activity, but also by stimulating polyamine uptake [, ]. AZIN2 may have a role in spermiogenesis [, ].
