Ornithine decarboxylase (ODC) antizyme protein that negatively regulates ODC activity and intracellular polyamine biosynthesis and uptake in response to increased intracellular polyamine levels. Binds to ODC monomers, inhibiting the assembly of the functional ODC homodimers. Does not target the ODC monomers for degradation, which allows a protein synthesis-independent restoration of ODC activity (By similarity). Involved in the translocation of AZIN2 from ER-Golgi intermediate compartment (ERGIC) to the cytosol (By similarity). Interacts with ODC1 and thereby sterically blocks ODC homodimerization (By similarity). Interacts with AZIN2; this interaction disrupts the interaction between the antizyme and ODC1 (By similarity). A ribosomal frameshift occurs between the codons for Ser-32 and Asp-33. An autoregulatory mechanism enables modulation of frameshifting according to the cellular concentration of polyamines. Belongs to the ODC antizyme family.