A cDNA (814 bp) encoding ornithine decarboxylase (ODC) antizyme (Az) was cloned from the Tobacco cutworm, Spodoptera litura. The open reading frame (ORF) showed an internal stop codon (TGA) on bases 223-224-225, encoding 270 amino acids except for the 223-T. A modified ODC Az cDNA (Slit ODC AzM) by point mutation for removal of the 223-T was introduced into a yeast (Saccharomyces cerevisiae) strain expressing a cloned ODC from the Tobacco cutworm. The transformed strain with ODC AzM exhibited a remarkable inhibition on ODC action, showing 56 % lowered cellular proliferation rate and the decreased cellular polyamine levels by 40.1 % (putrescine), 64.1 % (spermidine) and 58.6 % (spermine) at 48 hrs of cultivation in comparison with the original ODC Az cDNA. These results suggest that the modified ODC Az is expressed regardless of the frame-shifting and the expressed functional protein effectively inhibits the ODC activity.