DHODH inhibition Assay
DHODH enzymatic activity was determined using 2, 6-dichloroindophenol (DCIP) method as previously described(Diao et al., 2012). In brief, recombinant human DHODH (15 nM) was incubated with varied concentrations of indicated compounds for 10 min at room temperature. The assay buffer was composed of 50 mM Tris (pH 8.0), 120 μM DCIP, 100 μM Coenzyme Q0 (CoQ0), 0.1% Triton X-100. The enzymatic reaction was initiated by adding dihydroorotate (DHO) with a final concentration of 500 μM and absorption at 600 nm was continuously recorded for 6 min with EnVision Multimode Plate Reader (Perkin Elmer, ‎Waltham, MA). The IC50 values were calculated by GraphPad Prism 7 (GraphPad software, CA).