背景资料:Kidney amine oxidase (KAO), also called diamine oxidase (DAO) and amiloride-binding protein (ABP), is a member of the copper/topaquinone oxidase family. Notable compounds degraded by KAO include putrescine, histamine, spermine and spermidine, as well as substances involved in allergic and immune responses, cell proliferation, tissue differentiation, tumor formation, and possibly apoptosis. The secreted KAO protein can be detected in the extracellular space of placenta and kidney. Placental KAO is thought to play a role in the regulation of female reproductive function. KAO consists of two isoforms due to alternative splicing. Isoform 1 is the common 751 amino acid form while isoform 2 contains the additional 19 amino acids between residues 619 and 637.