The assay has been previously published . Briefly, 3 µL of enzyme (final concentration of 5 nM for ALDH3A1) or assay buffer (100 mM HEPES pH 7.5 with 0.01% Tween 20) were dispensed into a 1,536-well solid-bottom black plate. Twenty nL of compounds (final concentration range 420 pM to 50 µM) or control (DEAB or ZM-39923 final concentration range 1.52 nM to 50 µM) were transferred via acoustic droplet ejection. Samples were incubated (room temperature, protected from light) for 15 minutes followed by an addition of 1 µL substrate mixture of NADP + and benzaldehyde (final concentrations of 1 mM and 200 µM, respectively; Kms of 260 μM and 280 μM, respectively) , in addition to coupling reagents Resazurin and Diaphorase (final concentrations of 100 μM and 0.7 U/mL) to right-shift the detection by monitoring the production of resorufin . Plates were centrifuged at 1,000 rpm (164 x g) for 15 seconds, then read (RT) in kinetic mode on a ViewLux High-throughput CCD imager equipped with standard Rhodamine optics (525 nm excitation, 598 nm emission) for 5 minutes (< 20% conversion). The change in fluorescence intensity over the 5-minute reaction period was normalized against no-inhibitor and no-enzyme controls.