CHEMBL5736612

In Vitro Kinase Assay: The purpose of the BTK in vitro assay is to determine compound potency against BTK through the measurement of IC50. Compound inhibition is measured after monitoring the amount of phosphorylation of a fluorescein-labeled polyGAT peptide (Invitrogen PV3611) in the presence of active BTK enzyme (Upstate 14-552), ATP, and inhibitor. The BTK kinase reaction was done in a black 96 well plate (costar 3694). For a typical assay, a 24 pL aliquot of a ATP/peptide master mix (final concentration; ATP 10 μM, polyGAT 100 nM) in kinase buffer (10 mM Tris-HCl pH 7.5, 10 mM MgCl2, 200 μM Na3PO4, 5 mM DTT, 0.01% Triton X-100, and 0.2 mg/ml casein) is added to each well. Next, I pL of a 4-fold, 40× compound titration in 100% DMSO solvent is added, followed by adding 15 uL of BTK enzyme mix in 1× kinase buffer (with a final concentration of 0.25 nM). The assay is incubated for 30 minutes before being stopped with 28 pL of a 50 mM EDTA solution. Aliquots (5 uL) of the kinase reaction are transferred to a low volume white 384 well plate (Corning 3674), and 5 pL of a 2× detection buffer (Invitrogen PV3574, with 4 nM Tb-PY20 antibody, Invitrogen PV3552) is added. The plate is covered and incubated for 45 minutes at room temperature. Time resolved fluorescence (TRF) on Molecular Devices M5 (332 nm excitation; 488 nm emission; 518 nm fluorescein emission) is measured. IC50 values are calculated using a four parameter fit with 100% enzyme activity determined from the DMSO control and 0% activity from the EDTA control.