| Assay Method Information | |
| | KHK Enzyme Activity Assay for Human KHK-C and Human KHK-A |
| Description: | The intrinsic potency for inhibition of KHK C or A activity may be measured using an enzymatic assay which measures the production of FIP. Compounds are prepared in DMSO and tested in a 10-point concentration curve, to create 3-fold serial dilutions of the compounds in a 96-well plate ranging from 20 μM to 1.02 nM. Enzyme is prepared in assay buffer [50 mM 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 10 mM potassium chloride, 100 mM magnesium chloride, 2 mM tris(2-carboxyethyl)phosphine (TCEP), 0.01% n-octyl glucoside] and incubated with compounds at RT for 15 min. The reaction is carried out in 100 μL volumes containing substrate concentrations of fructose (250 μM for KHK-C assay and 1.25 mM for KHK-A assay) and ATP (150 μM for both isoforms); which are further incubated at RT for 20 min. The reaction is then halted by the addition of stop buffer; consisting of 0.2% formic acid and 1 μg/ml 13C6-fructose-6-phosphate (13C6-F6P) internal standard. Plates are stored in −20° C. until RapidFire MS analysis.RapidFire MS Analysis for Quantitation of F1PAn Agilent 300 RapidFire automated extraction system (Agilent, Santa Clara, Calif.) with three HPLC quaternary pumps is coupled to an Agilent 6495 triple quadrupole mass spectrometer (Agilent Technologies, Santa Clara, Calif.) equipped with an electrospray ionization (ESI) interface source. The RapidFire Mass Spec system is equipped with a reusable RapidFire C18 (type C) solid-phase extraction (SPE) cartridge (G9205 Å).Solvent A, used for sample loading and washing, is 6 mM octylamine (Acros Organics 129495000) brought to pH 5.0 using acetic acid. Solvent B, used for sample elution, is 20% water in ACN containing 0.1% formic acid. Samples are sequentially analyzed by aspirating 10 μL onto the collection loop under vacuum directly from multiwell plates. The 10 μL of sample is loaded onto the C18 cartridge and washed using solvent A at a flow rate of 1.25 mL/min for 5000 ms. The retained analytes are then eluted to the mass spectrometer using solvent B at a flow rate of 1.25 mL/min for 5000 ms. The system is re-equilibrated using solvent at flow rate of 1.25 mL/min for 2000 ms.The triple quadrupole mass spectrometer is equipped with an ESI source and analytes are monitored using selected reaction monitoring (SRM) in negative mode [M−H]−. F1P is monitored at m/z 259.02/96.9 and 13C6-fructose-6-phosphate is monitored at m/z 264.99/97. The area ratio values for F1P is calculated using 13C6-fructose-6-phospate as internal standard. |
| Affinity data for this assay | |
|---|---|
| If you find an error in this entry please send us an E-mail | |