High-throughput screening for phosphatidylserine decarboxylase inhibitors using a distyrylbenzene-bis-aldehyde (DSB-3)-based fluorescence assay.

Phosphatidylserine decarboxylases (PSDs) catalyze the decarboxylation of phosphatidylserine to generate phosphatidylethanolamine, a critical step in phospholipid metabolism in both prokaryotes and eukaryotes. Most PSDs are membrane-bound, and classical radioisotope-based assays for determining their activity are not suitable for high-throughput drug screening. The finding that the PkPSD from can be purified in a soluble and active form and the recent development of a fluorescence-based distyrylbenzene-bis-aldehyde (DSB-3) assay to measure PSD activity have laid the groundwork for screening chemical libraries for PSD inhibitors. Using this assay, here we conducted a high-throughput screen of a structurally diverse 130,858-compound library against PkPSD. Further characterization of the hits identified in this screening yielded five PkPSD inhibitors with IC values ranging from 3.1 to 42.3 μm Lead compounds were evaluated against the pathogenic yeast in the absence or presence of exogenous ethanolamine, and YU253467 and YU254403 were identified as inhibiting both native PSD mitochondrial activity and growth, with an MIC of 22.5 and 15 μg/ml without ethanolamine and an MIC of 75 and 60 μg/ml with ethanolamine, respectively. Together, these results provide the first proof of principle for the application of DSB-3-based fluorescent readouts in high-throughput screening for PSD inhibitors. The data set the stage for future analyses to identify more selective and potent PSD inhibitors with antimicrobial or antitumor activities.