PAOX belongs to the flavin monoamine oxidase family. PAOX is a flavoenzyme which catalyzes the oxidation of N(1)-acetylspermine to spermidine and is thus involved in the polyamine back-conversion. It can also oxidize N(1)-acetylspermidine to putrescine. PAOX does not oxidize spermidine. It plays an important role in the regulation of polyamine intracellular concentration and has the potential to act as a determinant of cellular sensitivity to the antitumor polyamine analogs.