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Assay Method Information

Assay Name:  ATX biochemical assay
Description:  ATX (Autotaxin) is a 125 KDa glycoprotein with lysophospholipase D (LPLD) activity that generates the bioactive lipid lysophosphatidic acid (LPA) from lysophosphatidylcholine (LPC). The ATX biochemical assay utilizes a FRET (fluorescence resonance energy transfer) technology platform. The fluorescence signal of FRET substrate FS-3 is quenched due to intra-molecular FRET of a fluorophore to a non-fluorescing quencher (Ferguson, C. G., et al., Org Lett. 2006 May 11; 8(10): 2023-2026, which is incorporated by reference in its entirety). ATX catalyzes the hydrolysis of the substrate which separates the dabsyl quencher from the fluorescein reporter, which becomes fluorescent. The reaction is monitored by a SpectraMax M5 (Molecular Devices, Sunnyvale, Calif.) with at excitation wavelength 485 nm and emission wavelength 535 nm.ReagentsFatty acid free-BSA (Sigma A8806): 10 mg/mL in H2O, stored at 4° C.2×ATX assay buffer: 100 mM Tris, 280 mM NaCl, 10 mM KCl, 2 mM CaCl2, 2 mM MgCl2, pH 7.4.Human ATX protein: expressed and purified in house. Stored at −80° C.Substrate FS-3 (Echelon, L-2000): 100 μg in 77.74 μL H2O (1 mM stock), stored at −20° C.384-well flat bottom plates Corning #3575.AssayCompound dilution All compounds were provided at 10 mM in 100% DMSO. In the first well, 2 μL of 10 mM compound was added to 78 μL of DMSO (1:40 dilution). In subsequent wells 3-fold dilution (total 10 dilutions) were performed.1×ATX assay buffer was made up with a final concentration of 1 mg/mL fatty acid free-BSA using 2×ATX assay buffer, 10 mg/ml fatty acid free-BSA and ddH2O.ATX protein was diluted with 1×ATX assay buffer to a concentration of 1.32 μg/mL (1.32×). 38 μL was added per well to the assay plate. The final concentration of ATX in the reaction as 1.0 μg/mL.2 μL per well of compounds was transferred to provide the desired concentration. The plate was centrifuged, then incubated at room temperature for 30 minutes on the shaker.FS-3 was diluted with 1×ATX assay buffer to a concentration of FS-3 of 10 μM (5×). Then, 10 μL was added per well to the assay plate. The final concentration of FS-3 in the reaction was 2 μM. The plate was centrifuged. The plate was kept shaking at room temperature for 2 hours. Because FS-3 substrate is light sensitive, plates were kept covered and protected from light.Fluorescence was measured using SpectraMax M5 (excitation at 485 nm/emission at 538 nm, top read).
Affinity data for this assay
 

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Last update November 1, 2007
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