CHEMBL5737841

Enzyme Inhibition Assay: Enzyme inhibition studies were performed using recombinant JAK1 (amino acids 866-1154, Life Technologies, #PV4774, Carlsbad, Calif.), JAK2 (amino acids 831-1132), or JAK3 (amino acids 781-1124) under buffer conditions of 50 mM HEPES pH 7.3, 1 mM DTT, 0.01% Tween® 20, 50 μg/mL BSA, and 10 mM MgCl2. JAK enzyme was expressed as an N-terminal GST fusion in insect cells and purified by glutathione-affinity and size-exclusion chromatographies. Enzymes were assayed both at their respective ATP Km (JAK1: 55 μM, JAK2: 15 μM, JAK3: 3 μM) and the approximated high end of physiological ATP concentration of 5 mM, in the presence of inhibitor dosed at 30, 3, 0.3, 0.03, 0.003 and 0 μM final test concentrations. For JAK1, 6 nM of enzyme (for Km ATP assay) or 4 nM enzyme (for high ATP assay) was incubated with 1.5 μM peptide substrate (FITC-C6-KKHTDDGYMPMSPGVA-NH2 (SEQ ID NO:1), Intonation, Boston, Mass.). For JAK2, 0.8 nM of enzyme (for Km ATP assay) or 0.3 nM enzyme (for high ATP assay) was incubated with 1.5 μM peptide substrate (5FAM-GEEPLYWSFPAKKK-NH2 (SEQ ID NO:2), Intonation, Boston, Mass.). For JAK3, 0.2 nM of enzyme (for Km ATP assay) or 0.1 nM enzyme (for high ATP assay) was incubated with 1.5 μM peptide substrate (5FAM-GEEPLYWSFPAKKK-NH2 (SEQ ID NO:2), Intonation, Boston, Mass.). Phosphorylated and unphosphorylated peptides were separated and quantified by a Caliper LC3000 system (Caliper Life Sciences, MA) for calculating percent inhibition.