Assay Method Information

Assay Name:  Biochemical Assay
Description:  IDH1-R132H, IDH1-R132C, IDH2-R172K and IDH2-R140Q mutant enzymes catalyze the conversion of αKG to 2HG. 2HG is analyzed using in-line solid phase extraction and mass spectrometry. This analysis is carried out in a RapidFire instrument coupled to a 6460 triple quadrupole mass spectrometer (G6460A Agilent).IDH1 mutant (R132H and R132C) and IDH2 mutant (R140Q and R172K) proteins containing N-terminal His-tag are expressed in E.coli and purified using nickel affinity chromatography. The enzyme assays are carried out in V-bottom 96 well polypropylene plates containing 100 mM Tris-HCl buffer, 1 mM DTT, 0.005% TRITON X-100, 120 mM NaCl. For IDH1 R132H, α-ketoglutarate, NADPH and MnCl2 are included at final concentrations of 300 μM, 2.5 μM and 300 μM respectively. For IDH1 R132C, α-ketoglutarate, NADPH and MnCl2 are included at final concentrations of 100 μM, 10 μM and 100 μM respectively. For IDH2 R172K, α-ketoglutarate, NADPH and MnCl2 are included at final concentrations of 150 μM, 10 μM and 150 μM respectively. For IDH2 R140Q, α-ketoglutarate, NADPH and MnCl2 are included at final concentrations of 3000 μM, 10 μM and 100 μM respectively. Final pH=7.0. Test compound dissolved in DMSO stock is diluted in the reaction mix at a final DMSO concentration of 4%. Compounds are tested in dose-response format. The assay is started by addition of enzyme. Enzymes are used at the following final concentrations: IDH1 R132H, 2 nM; IDH1 R132C, 0.5 nM; IDH2 R172K, 1.2 nM; IDH2 R140Q, 1.2 nM. After 90 minutes the reaction is quenched by adding ACN (50:50) containing 3-hydroxy-1,5-pentanedioic-2,2,3,4,4-d5 acid (5d5-3HG) as an internal standard for mass spectrometry analysis and quantitation of reaction product. 2-Hydroxyglutarate (2HG) in quenched samples is separated using strong anionic exchange column chromatography (Phenomenex Strata-X-A SecurityGuard) and analyzed by mass spectrometry in a 6460 triple quadrupole mass spectrometer (G6460A Agilent). The 2HG signal detected is transformed into an analyte concentration using a calibration curve generated using known 2HG concentrations. For each compound tested, the % inhibition is calculated using a DMSO control sample as 0% inhibition and a no enzyme control as 100% inhibition.
Affinity data for this assay
 

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