| Assay Method Information | |
| | Inhibition of Tautomerase Activity of Human MIF |
| Description: | Inhibition of the tautomerase activity of MIF was measured using 4-hydroxyphenyl pyruvic acid (HPP) as substrate, largely following previously reported protocols (Taylor et al., Biochemistry, 1999, 38, 7444-7452). HPP was dissolved in 0.5 M acetate buffer, pH 6.0 to a final concentration of 10 mM and incubated overnight at room temperature to allow equilibration of the keto and enol forms. MIF (6 μL) was premixed in 500 mM boric acid, pH 6.2 (142 μL) and transferred to a transparent U bottom 96-well plate to a final concentration of 50 nM MIF. At this concentration high signal-to-noise and linearity were observed after analysis of progress curves for enol production at different protein concentrations. Inhibitors were dissolved in DMSO to 10 mM and an initial screen was performed. For compounds that showed ca. 25% or greater inhibition at 10 μM, an inhibition constant, was measured.Compounds were placed into wells (2 μL) at 6 different concentrations and incubated for 30 minutes until the assay was started by addition of HPP (504) at two concentrations (1.0 and 2.5 mM). The negative control was MIF incubated with DMSO vehicle, which in all assays was 1% and did not influence tautomerase activity. MIF activity was monitored at 305 nm for formation of the borate-enol complex using an Infinite F500 plate reader (TECAN, Morrisville, N.C.) for 175 seconds. Calculation of initial velocities and the nonlinear regression analyses for the enzyme kinetics were repeated three times with the program Prism6 (GraphPad, La Jolla, Calif.).Data obtained for the Example compounds, obtained using the methods described in Example B, are provided in Table 3. Results are also included for a reference compound ISO-1 (Chang, K. F.; Al-Abed, Y. Bioorg. Med. Chem. Lett. 2006, 16, 3376-3379; Balachandran, S. et al. Bioorg. Med. Chem. Lett. 2009, 19, 4773-4776). X-ray crystal structures were obtained for complexes of 3a, 3b, and 3v (Examples 1, 2, and 21) with human MIF as described below in Example C, which confirm the binding of these inhibitors in the tautomerase active site. |
| Affinity data for this assay | |
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