Diamine oxidase

Synonym(s)

DAO; Histaminase

Definition
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Copper-containing enzyme that is essential for the degradation of histamine and other biogenic amines (e.g. cadaverine, dopamine, phenethylamine, putrescine, serotonin, tyramine, noradrenaline). The enzyme is produced by enterocytes. The activity of the diamine oxidase defines the degradation rate and thus the elimination of biogenic amines (especially histamine). A lack of DAO or a reduced biological activity leads to intolerance phenomena on biogenic amines (see below histamine intolerance). Causes can be gastrointestinal diseases, e.g. gastrointestinal infections, a lack of trace elements as well as rare congenital enzyme defects. DAO-inhibitors are alcohol and various drugs. Drugs (see below histamine intolerance). In the case of histamine intolerance, in addition to reduced DAO activity, increased histamine values and low vitamin B6 (vitamin B6 acts as a co-factor) and copper (enzyme contains copper) levels are often found.

Implementation
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The DAO determination is carried out in EDTA plasma or serum (stored cool 2-8°C); minimum sample volume 2 ml. Samples stored in a cool place are stable for a maximum of one week and can be sent by mail in a Thermo-Styropor-Bag. Important: Freshly collected samples (plasma or serum) must be centrifuged and stored in a cool place immediately after blood collection. Evaluation:

DAO < 3 U/ml: very low enzyme activity
DAO 3 - 10 U/ml: average enzyme activity
DAO > 10 U/ml: normal enzyme activity.

Note(s)
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Alcohol inhibits the enzyme activity of DAO, simultaneously enhances the absorption of histamine, and induces a non-IgE-mediated release of histamine from mast cells and basophils.