This entry consists of various amine oxidases, including maize polyamine oxidase (PAO) [<cite idref="PUB00001716"/>], L-amino acid oxidases (LAO) and various flavin containing monoamine oxidases (MAO). The aligned region includes the flavin binding site of theseenzymes.In vertebrates MAO plays an important role in regulating the intracellular levels of amines via their oxidation; these include various neurotransmitters, neurotoxins and trace amines [<cite idref="PUB00002991"/>]. In lower eukaryotessuch as aspergillus and in bacteria the main role of amine oxidases is to provide a source of ammonium [<cite idref="PUB00003770"/>].PAOs in plants, bacteria and protozoa oxidise spermidine and spermine to an aminobutyral, diaminopropane and hydrogen peroxide and are involved in the catabolism of polyamines [<cite idref="PUB00001716"/>].Other members of this family include tryptophan 2-monooxygenase, putrescine oxidase, corticosteroid binding proteins and antibacterial glycoproteins. Amine oxidase