Assay Method Information

Assay Name:  Inhibition of ENPP1 Hydrolysis of 2′,3′-cGAMP
Description:  Assay 2: Compared to the conditions in Assay 1, this assay has a larger dynamic range and ensures the system is under steady-state conditions by reducing the enzyme concentration in the assay. This allows discrimination among very potent compounds and allows for conversion of IC50 data to KIs.Test compounds were plated in a 3× dilution scheme in a 384 well plate. To 50 nL of test compound in DMSO was added 2.5 μL ENPP-1 ECD in Assay Buffer (Tris-HCl pH 8.0 (50 mM), NaCl (150 mM), and 0.01% Triton X-100 in water (0.25 nM final ENPP-1 concentration). Enzyme was omitted in control wells reserved to define maximum inhibition (max). Control wells were reserved to define no inhibition (min), and DMSO was used in place of compound solution. The plate was centrifuged for 30 s, and the mixture was incubated for 30 min. 2.5 μL of 2,3-cGAMP in Assay Buffer (final conc: 24 μM; KM=24 μM) was added and the plate was centrifuged and incubated for 30 min. AMP-Glom Reagent I (Promega Corp.; 5 μL) was added, the plate was centrifuged for 1 min and incubated for 60 min. AMP Detection solution (10 μL) was added to each well, the plate centrifuged and incubated for 60 min. Luminescence was measured with an Envision plate reader, and % Inhibition was calculated for each well as: (([max −min]−[test−min])/[max−min].
Affinity data for this assay
 

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