A discontinuous luminometric assay for monoamine oxidase.

Abstract A simple, sensitive and convenient discontinuous luminometric assay for monoamine oxidase (MAO) is described. It is based on measurement of the light production from the peroxjdase-catalysed chemiluminescent oxidation of 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) by the hydrogen peroxide produced in the MAO reaction. The procedure is suitable for use with a wide range of MAO substrates, although 5-hydroxytryptamine, adrenaline and noradrenaline are too readily oxidized by hydrogen peroxide to be used. A particular advantage of this procedure is that it is applicable to the oxidation of substrates which do not yield products, such as an aldehyde or free ammonia, which form the basis of several alternative substrate-independent assay procedures. The application of the procedure to assay the oxidation of benzylamine, tyramine and 2- n -pentylaminoacetamide (milacemide) by a crude mitochondrial preparation from rat liver and purified ox liver MAO-B is demonstrated.