Assay Method Information

Assay Name:  In Vitro Enzyme Inhibition Assay
Description:  This assay determines the ability of a test compound to inhibit LSD1 demethylase activity. E. coli expressed full-length human LSD1 (Accession number O60341) was purchased from Active Motif (Cat#31334).The enzymatic assay of LSD1 activity is based on Time Resolved-Fluorescence Resonance Energy Transfer (TR-FRET) detection. The inhibitory properties of compounds to LSD1 were determined in 384-well plate format under the following reaction conditions: 0.1-0.5 nM LSD1, 50 nM H3K4me1-biotin labeled peptide (Anaspec cat #64355), 2 μM FAD in assay buffer of 50 mM HEPES, pH7.3, 10 mM NaCl, 0.005% Brij35, 0.5 mM TCEP, 0.2 mg/ml BSA. Reaction product was determined quantitatively by TR-FRET after the addition of detection reagent Phycolink Streptavidin-allophycocyanin (Prozyme) and Europium-anti-unmodified histone H3 lysine 4 (H3K4) antibody (PerkinElmer) in the presence of LSD1 inhibitor such as 1.8 mM of Tranylcypromine hydrochloride (2-PCPA) in LANCE detection buffer (PerkinElmer) to final concentration of 12.5 nM and 0.25 nM respectively.The assay reaction was performed according to the following procedure: 2 μL of the mixture of 150 nM H3K4me1-biotin labeled peptide with 2 μL of 11-point serial diluted test compound in 3% DMSO were added to each well of plate, followed by the addition of 2 μL of 0.3 nM LSD1 and 6 μM of FAD to initiate the reaction. The reaction mixture was then incubated at room temperature for one hour, and terminated by the addition of 6 μL of 1.8 mM 2-PCPA in LANCE detection buffer containing 25 nM Phycolink Streptavidin-allophycocyanin and 0.5 nM Europium-anti-unmodified H3K4 antibody. Enzymatic reaction is terminated within 15 minutes if 0.5 LSD1 enzyme is used in the plate. Plates were read by EnVision Multilabel Reader in TR-FRET mode (excitation at 320 nm, emission at 615 nm and 665 nm) after 1 hour incubation at room temperature. A ratio was calculated (665/615) for each well and fitted to determine inhibition constant (IC50).
Affinity data for this assay

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