A colorimetric method for the estimation of monoamine oxidase

Abstract
A method is described for the estimation of monoamine oxidase based on measurement of the aldehyde formed during the enzymic oxidation of tyramine. The unstable aldehyde is prevented from decomposing by the presence of semicarbazide in the assay mixture. The semicarbazone so formed is then converted into the corresponding 24-dinitrophenyl-hydrazone. The color of this material in alkaline solution provides a sensitive measure of the enzymic activity.