Structural, kinetic, and pharmacodynamic mechanisms of D-amino acid oxidase inhibition by small molecules.

Seth C Hopkins, Michele L R Heffernan, Lakshmi D Saraswat, Carrie A Bowen, Laurence Melnick, Larry W Hardy, Michael A Orsini, Michael S Allen, Patrick Koch, Kerry L Spear, Robert J Foglesong, Mustapha Soukri, Milan Chytil, Q Kevin Fang, Steven W Jones, Mark A Varney, Aude Panatier, Stephane H R Oliet, Loredano Pollegioni, Luciano Piubelli, Gianluca Molla, Marco Nardini, Thomas H Large

Index: J. Med. Chem. 56(9) , 3710-24, (2013)

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Abstract

We characterized the mechanism and pharmacodynamics of five structurally distinct inhibitors of d-amino acid oxidase. All inhibitors bound the oxidized form of human enzyme with affinity slightly higher than that of benzoate (Kd ≈ 2-4 μM). Stopped-flow experiments showed that pyrrole-based inhibitors possessed high affinity (Kd ≈ 100-200 nM) and slow release kinetics (k < 0.01 s(-1)) in the presence of substrate, while inhibitors with pendent aromatic groups altered conformations of the active site lid, as evidenced by X-ray crystallography, and showed slower kinetics of association. Rigid bioisosteres of benzoic acid induced a closed-lid conformation, had slower release in the presence of substrate, and were more potent than benzoate. Steady-state d-serine concentrations were described in a PK/PD model, and competition for d-serine sites on NMDA receptors was demonstrated in vivo. DAAO inhibition increased the spatiotemporal influence of glial-derived d-serine, suggesting localized effects on neuronal circuits where DAAO can exert a neuromodulatory role.