Spectrophotometric Assay of Monoamine Oxidase Using 2, 4, 6-Trinitrobenzene-1-sulfonic Acid

Abstract

A new spectrophotometric assay method of monoamine oxidase [EC 1.4.3.4] was developed. The method is based on the principle that the absorbance at 422 mμ increases in the reaction of monoamine with 2, 4, 6-trinitrobezene-1-sulfonic acid at pH 8. This assay method is very sensitive, because the molar extinction coefficients of trinitrophenylated monoamine derivatives are high, being the order of 10⁴ M⁻¹ cm⁻¹, while trinitrophenylation of ammonia gives a derivative with a much lower coefficient. In contrast to other methods commonly employed, this method is applicable to the assay of various monoamines, and is not disturbed by the oxygen consumption in monoamine oxidase assay.