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. Stabilizes AZIN2 by interfering with its ubiquitination. Involved in the translocation of AZNI2 from ER-Golgi intermediate compartment (ERGIC) to the cytosol. Probably plays a key role in spermatogenesis by regulating the intracellular concentration of polyamines in haploid germ cells (By similarity). Does not possess antizyme activity. Modulates PPP1CB activity through its interaction with PPP1R16A. 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). Interacts with GGN (By similarity). Isoform 2 interacts with PPP1R16A; Modulates PPP1CB activity (PubMed:21712390). Testis-specific. Isoform 2 is expressed in outer dense fibers, fibrous sheath and the connecting piece of sperm (PubMed:21712390). PubMed:17040916 reports an event of trans-splicing that creates a hybrid 14-kDa protein whose N-terminal 105 amino acids are encoded by the rat Oaz3 gene, located on chromosome 2 and its C-terminal 33 amino acids by a novel gene located on chromosome 4. The nuclear pre-mRNA of Oaz3 gene has 5 adenosine residues whereas the nuclear trans-spliced RNA has 6 adenosine residues suggesting that an unknown nuclear process adds 1 adenosine affecting the reading frame. Moreover the hybrid 14-kDa protein is the result of ribosomal frameshift. The hybrid 14-KDa protein is present in the outer dense fibers and the fibrous sheath and expressed in lung. Produced by ribosomal frameshifting occurring between the codons for Ser-86 and Glu-87. An autoregulatory mechanism enables modulation of frameshifting according to the cellular concentration of polyamines. Produced by alternative splicing. This form is not the result of ribosomal frameshift. Belongs to the ODC antizyme family. Unusual initiator. The initiator methionine is coded by a non-canonical CTG leucine codon.