engleski

A simple fluorimetric assay for measuring kinetics of monoamine oxidase: comparison of brain and platelets

Monoamine oxidase (MAO) is a mitochondrial enzyme that catalyses oxidative deamination of various physiologically important biogenic amines, especially neurotransmitters such as serotonin, adrenaline, histamine and dopamine. In most mammalian tissues there are two forms of MAO, type A (MAO-A) and type B (MAO-B), differing in their affinities toward substrates and sensitivity to inhibitors, while very few tissues express only one form of the enzyme. MAO kinetic follows Michaelis-Menten model. A simple fluorimetric method for determination of kinetic parameters (Vmax and Km) of MAO in human platelets and rat brain has been described. The method uses a nonspecific substrate, kynuramine, which is converted by both types of MAO to 4-hydroxyquinoline which fluoresces in alkaline solution. This method has been used previously with platelets that contain only one type of MAO (MAO-B), and here we adjusted the method for the use with brain tissue where both types of MAO are present. In order to determine Vmax and Km of the single isoenzyme in the brain, the other one has to be specifically inhibited: MAO-A by clorgyline and MAO-B by deprenyl. The described method is low-cost, simple and reproducible and may represent a method of choice for measuring MAO saturation kinetics in various tissues.

monoamine oxidase

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