Slow-binding human serine racemase inhibitors from high-throughput screening of combinatorial libraries

One-bead one-compound combinatorial chemistry together with a high-throughput screen based on fluorescently labeled enzyme allowed the identification of slow binding inhibitors of human serine racemase (hSR). A peptide library of topographically segregated encoded resin beads was synthesized, and several hSR-binding compounds were isolated, identified, and resynthesized for further kinetic study. Of these, several showed inhibitory effects with moderate potency (high micromolar K_Is) toward hSR. A clear structural motif was identified consisting of 3-phenylpropionic acid and histidine moieties. Importantly, the inhibitors identified showed no structural similarities to the natural substrate, L-serine. Detailed kinetic analyses of the properties of selected inhibitors show that the screening protocol used here selectively identifies slow binding inhibitors. They provide a pharmacophore for the future isolation of more potent ligands that may prove useful in probing and understanding the biological role of hSR.