Inhibition of D-amino acid oxidase activity by antipsychotic drugs evaluated by a fluorometric assay using D-kynurenine as substrate.

A facile fluorometric assay using D-kynurenine as a substrate was utilized for evaluating the inhibition of D-amino acid oxidase (DAAO), which is one of the products of a susceptibility gene for schizophrenia, by commercial antipsychotic drugs, namely, chlorpromazine (CPZ), carbamazepine, sulpiride, quetiapine, and imipramine. CPZ inhibited DAAO (65.8 ± 13.2 µM, n = 3) as reported previously, and other drugs also inhibited DAAO activity. Among these, quetiapine had the smallest IC(50) value (19.5 ± 2.60 µM, n = 3). The proposed assay can be useful for the evaluation or screening of DAAO-inhibitory drugs.