PTP pNPP Assay: PTP activity was assayed using p-nitrophenyl phosphate (pNPP) as a substrate in DMG buffer (50 mM DMG, pH 7.0, 1 mM EDTA, 150 mM NaCl, 2 mM DTT, 0.1 mg/mL BSA) at 25° C. The assays were performed in 96-well plates. Normally, to determine the IC50 values, the reaction was initiated by the addition of enzyme (final concentration of 10 nM) to a reaction mixture (0.2 mL) containing 2 mM (Km for the substrate) pNPP with various concentrations of inhibitors. The reaction rate was measured using a Spectra Max Plus 384 Microplate Spectrophotometer (Molecular Devices). For compound 10, the final TC-PTP concentration was 0.04 nM. The reactions were incubated at room temperature for 30 min and quenched with 5N NaOH. The absorbance at 405 nm was read on the SpectraMax Plus 384 Microplate Spectrophotometer. For the reversibility test, the enzyme was incubated with the inhibitor at room temperature for 30 min before pNPP was added to initiate the reaction. The reaction was then incubated at room temperature.
Enzyme Kinetic Assay: PTP activity was assayed using p-nitrophenyl phosphate (pNPP) as a substrate in 3,3-dimethylglutarate buffer (50 mM 3,3-dimethylglutarate, pH 7.0, 1 mM EDTA, 150 mM NaCl, 2 mM DTT, 0.1 mg/mL BSA) at 25° C. The assays were performed in 96-well plates. Normally, to determine the IC50 values, the reaction was initiated by the addition of enzyme (final concentration at 10 nM) to a reaction mixture (0.2 mL) containing 2 mM (Km for the substrate) pNPP with various concentrations of inhibitors. The reaction rate was measured using a SpectraMax Plus 384 Microplate Spectrophotometer (Molecular Devices). To determine the mode of inhibition, the reactions were initiated by the addition of PTP-MEG2 to the reaction mixtures (0.2 mL) containing various concentrations of pNPP with different concentrations of the inhibitor 7.
Inhibition of LMWPTP (unknown origin) using DiFMUP as substrate incubated for 30 mins followed by substrate addition at pH 6.5 by standard phosphatase assay based fluorescence analysis
Inhibition of LMWPTP (unknown origin) using DiFMUP as substrate at 100 uM incubated for 30 mins followed by substrate addition at pH 6.5 by standard phosphatase assay based fluorescence analysis
Inhibition of DUSP22 (unknown origin) pre-incubated for 20 mins followed by fluorescence substrate addition and measured after 120 mins by DiFMUP assay