Inhibition Assay: Mtb PDH (Lpd+DlaT+AceE) is provided by Dr. Bryk Ruslana. The assay was performed in a manner similar to that described in Bryk et al., Biochemistry (2010) 49:1616-1627 and modified for an online robotics screening system.A solution containing PDH (Lpd=15 μM; DlaT=30 μM; AceE=15 μM) was diluted 2-fold in 100 mM of potassium phosphate buffer (pH 7.0) for the assay. Another reaction solution containing 50 mM potassium phosphate buffer (pH 7.0), 200 μM TPP, 2 mM Pyruvate, 200 μM CoA, 1 mM MgCl2, 1 mM NAD+ was prepared. 5 μL/well of PDH solution was dispensed into 1536-well black plates. Next, 50 nL of each test compound (1 mM dissolved in DMSO) was added into each well. After 30 minutes of incubation, 5 μL/well of reaction solution was added. At the 30th minutes of the reaction, the florescence signal (excitation 360 nm and emission 460 nm) was obtained by Viewlux reader (PerkinElmer).
Inhibition Assay: The assay was performed in a manner similar to that described in Bryk et al., Biochemistry (2010) 49:1616-1627 and modified for an online robotics screening system.A solution containing Lpd (100 nM) and 100 mM sodium phosphate buffer (pH 7.0) was prepared. Another solution containing the substrate lipoamide (2 mM), 100 mM sodium phosphate buffer (pH 7.0), EDTA (4 mM), and NADH (200 uM) was also prepared. The detection reagent, DTNB was dissolved in DMSO and diluted to a concentration of 375 uM with a 100 mM sodium phosphate buffer (pH 7.0).4 uL/well of Lpd solution was dispensed into 1536-well clear bottom plates. Next, 50 nL of each test compounds (1 mM dissolved in DMSO) was added into each well. After one hour of incubation, 4 uL/well of lipoamide (LPA) solution was added, so that in each well, the concentrations of Lpd, LPA, and the test compound were 50 nM, 1 mM, and 6.25 uM, respectively.