| Assay Method Information | |
| | Biochemical Inhibition Assay |
| Description: | NAMPT Protein Purification. Recombinant His-tagged NAMPT was produced in E. coli cells, purified over a Ni column, and further purified over a size-exclusion column by XTAL Biostructures.The NAMPT Enzymatic Reaction. The NAMPT enzymatic reactions were carried out in Buffer A (50 mM Hepes pH 7.5, 50 mM NaCl, 5 mM MgCl2, and 1 mM THP) in 96-well V-bottom plates. The compound titrations were performed in a separate dilution plate by serially diluting the compounds in DMSO to make a 100× stock. Buffer A (89 μL) containing 33 nM of NAMPT protein was added to 1 μL of 100× compound plate containing controls (e.g. DMSO or blank). The compound and enzyme mixture was incubated for 15 min at room temperature, then 10 μL of 10× substrate and co-factors in Buffer A were added to the test well to make a final concentration of 1 μM NAM, 100 μM 5-Phospho-D-ribose 1-diphosphate (PRPP), and 2.5 mM Adenosine 5′-triphosphate (ATP). The reaction was allowed to proceed for 30 min at room temperature, then was quenched with the addition of 11 μL of a solution of formic acid and L-Cystathionine to make a final concentration of 1% formic acid and 10 μM L-Cystathionine. Background and signal strength was determined by addition (or non-addition) of a serial dilution of NMN to a pre-quenched enzyme and cofactor mix.Quantification of NMN. A mass spectrometry-based assay was used to measure the NAMPT reaction product, β-nicotinamide mononucleotide (NMN), and the internal control (L-Cystathionine). NMN and L-Cystathionine were detected using the services of Biocius Lifesciences with the RapidFire system. In short, the NMN and L-Cystathionine were bound to a graphitic carbon cartridge in 0.1% formic acid, eluted in 30% acetonitrile buffer, and injected into a Sciex 4000 mass spectrometer. The components of the sample were ionized with electrospray ionization and the positive ions were detected. The Q1 (parent ion) and Q3 (fragment ion) masses of NMN were 334.2 and 123.2, respectively. The Q1 and Q3 for L-Cystathionine were 223.1 and 134.1, respectively. The fragments are quantified and the analyzed by the following methodDetermination of IC50 Values. First, the NMN signal was normalized to the L-Cystathionine signal by dividing the NMN signal by the L-Cystathionine signal for each well. The signal from the background wells were averaged and subtracted from the test plates. The compound treated cells were then assayed for percent inhibition by using this formula:% Inh=100−100*x/ywherein x denotes the average signal of the compound treated wells and y denotes the average signal of the DMSO treated wells.IC50 values were then determined using the following formula:IC 50=10{circumflex over ( )}(LOG10(X)+(((50-%Inh at Cmpd Concentration 1)/(XX−YY)*(LOG10(X)−LOG10(Y))))wherein X denotes the compound concentration 1, Y denotes the compound concentration 2, XX denotes the % inhibition at compound concentration 1 (X), and YY denotes the % inhibition at compound concentration 2 (Y). |
| Affinity data for this assay | |
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