CHEMBL5733729

GLS Enzyme Potency Assay: A Glutamate Oxidase/AmplexRed coupled assay was used to measure the ability of compounds to bind to and inhibit the activity of GLS1 in vitro. 6His tagged GLS protein (amino acids 63-669) expressed in E. Coli was purified and stored at −80° C. in aliquots. GLS1 was diluted to 2× working concentration and incubated at r.t. to allow the tetrameric/dimeric forms to reach steady state. Assay measurements were performed in buffer comprising 50 mM TRIS pH 7.8, 100 mM NaPO4, pH 7.8, 0.001% v/v Tween20. Purified recombinant GLS1 protein was diluted in assay buffer to 12 nM and pre-incubated at r.t. for 30 minutes. Test compounds were prepared by dilution in 100% DMSO to give the correct dose range for 12 point concentration response and an appropriate volume (2.5-60 nl) dispensed into 384 well micro assay plates (Greiner product code 784900) using a Labcyte Echo 555 acoustic dispenser. DMSO concentration was maintained at 2% by back filling with DMSO solution. 3 μL of diluted GLS1 protein (12 nM) was then dispensed into each well using a BioRaptr automated dispenser (Beckman-Coulter) and incubated for 15 minutes at r.t. 3 μL of 100 mM glutamine diluted in assay buffer was then added and the reaction incubated at r.t. for 60 minutes. The reaction was then stopped by addition of 45 μM 6-(2-bromoethynyl)-2,3-dimethyl-quinazolin-4-one, 75 μM Amplex Red, 0.375 units/mL Horseradish Peroxidase, 0.12 units/mL Glutamate Oxidase in 100 mM TRIS pH7.5. After 30 minutes at room temp in the dark, plates were read on a Perkin Elmer EnVision using 535/590 nm optic filters and raw data analysed using Genedata to generate IC50 values. An artefact version of the assay where the 6His tagged GLS protein and glutamine were replaced with assay buffer was also used to rule out non specific effects on the assay components.