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Assay Method Information

Assay Name:  Monoamine Oxidase Assays for Determining the Selectivity of the Compounds of the Invention for LSD1
Description:  Human recombinant monoamine oxidase proteins MAO-A and MAO-B were purchased from Sigma Aldrich. MAOs catalyze the oxidative deamination of primary, secondary and tertiary amines. In order to monitor MAO enzymatic activities and/or their inhibition rate by inhibitor(s) of interest, a fluorescent-based (inhibitor)-screening assay was set up. 3-(2-Aminophenyl)-3-oxopropanamine (kynuramine dihydrobromide, Sigma Aldrich), a non fluorescent compound was chosen as a substrate. Kynuramine is a non-specific substrate for both MAOs activities. While undergoing oxidative deamination by MAO activities, kynuramine is converted into 4-hydroxyquinoline (4-HQ), a resulting fluorescent product.The monoamine oxidase activity was estimated by measuring the conversion of kynuramine into 4-hydroxyquinoline. Assays were conducted in 96-well black plates with clear bottom (Corning) in a final volume of 100 μL. The assay buffer was 100 mM HEPES, pH 7.5. Each experiment was performed in triplicate within the same experiment.Briefly, a fixed amount of MAO (0.25 μg for MAO-A and 0.5 μg for MAO-B) was incubated on ice for 15 minutes in the reaction buffer, in the absence and/or in the presence of various concentrations of inhibitor (e.g., from 0 to 50 μM, depending on the inhibitor strength). Tranylcypromine (Biomol International) was used as a control for inhibition.After leaving the enzyme(s) interacting with the inhibitor, 60 to 90 μM of kynuramine was added to each reaction for MAO-B and MAO-A assay respectively, and the reaction was left for 1 hour at 37 C. in the dark. The oxidative deamination of the substrate was stopped by adding 50 μL (v/v) of NaOH 2N. The conversion of kynuramine to 4-hydroxyquinoline, was monitored by fluorescence (excitation at 320 nm, emission at 360 nm) using a microplate reader (Infinite 200, Tecan). Arbitrary units were used to measure levels of fluorescence produced in the absence and/or in the presence of inhibitor.The maximum of oxidative deamination activity was obtained by measuring the amount of 4-hydroxyquinoline formed from kynuramine deamination in the absence of inhibitor and corrected for background fluorescence in the absence of MAO enzymes.
Affinity data for this assay
 

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Last update November 1, 2007
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