The Peroxidase-Coupled Assay to Measure MAO Enzymatic Activity

MAO activity measurement is generally performed following different spectroscopy methods, in most cases using peroxidase as a coupled reaction catalyst. In the presence of horseradish peroxidase (HRP), the assay follows the oxidation of the typical MAO substrate (aromatic amines) which generates hydrogen peroxide as a secondary product. There are several chromogens and fluorogens that, in the presence of hydrogen peroxide, are converted by HRP to detectable products. In the present chapter we describe the spectrophotometric 4-aminoantipyrine assay as well as the fluorogenic assay with the Amplex® Red chemical probe. These methods are applied on MAO activity and Michaelis-Menten curve determinations as well as inhibitory activity experiments.