Structural, Kinetic, and Pharmacodynamic Mechanisms of d‑Amino Acid Oxidase Inhibition by Small Molecules

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 (<i>K</i>_d ≈ 2–4 μM). Stopped-flow experiments showed that pyrrole-based inhibitors possessed high affinity (<i>K</i>_d ≈ 100–200 nM) and slow release kinetics (<i>k</i> < 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