Polyamines, including spermine, spermidine, putrescine, and agmatine, are polycationic alkylamines involved in various cellular functions like cell cycle regulation, scavenging reactive oxygen species, and gene expression control. They also impact neurotransmission by regulating receptor activity, intracellular signaling, and potentially acting as neurotransmitters. This gene encodes an FAD-containing enzyme that oxidizes spermine to spermidine, producing hydrogen peroxide as a byproduct. Multiple transcript variants encoding different isoenzymes have been identified, some of which show little oxidase activity on natural polyamine substrates. Characterized isoenzymes have distinct biochemical properties and substrate specificities, suggesting complexity in polyamine catabolism.