Characterization of Human Diamine Oxidase Produced in CHO

摘要

Human diamine oxidase (hDAO, E.C. 1.4.3.6), formerly termed histaminase and amiloride-binding protein 1 (ABP1), is encoded by the AOC1 gene and belongs to the group of copper-containing amine oxidases (CAOs). These enzymes are found in bacteria, yeast, plants and mammalians and deaminate primary amines to the corresponding aldehydes, ammonia and hydrogen peroxide. Natural substrates of hDAO include histamine and polyamines like pu-trescine, cadaverine and spermidine. It is an important enzyme in the extracellular catabolism of exogenous or endogenous histamine. High expression levels of hDAO are detected in the gastrointestinal tract, kidney and placenta. In addition to increased absorption of histamine an impaired function, decreased production or competitive inhibition of hDAO are suggested to contribute to histamine intolerance. The enzyme is a homodimer of 170 kDa and is highly gly-cosylated. Each active monomer contains one Cu (II) ion, as well as a TPQ (topaquinone) co-factor. Each subunit carries two further cation-binding sites, presumably for Ca2+, with yet unknown function.