Utilization of Kynurenic Acid Produced from D-kynurenine in an in Vitro Assay of D-Amino Acid Oxidase Activity

Evaluation of human D-amino acid oxidase inhibition by anti-psychotic drugs in vitro

“…The excitation and emission spectra of the product generated by the enzymatic reaction of hDAO with D-KYN were consistent with those of KYNA (15), and the increase in fluorescence intensity was dependent on reaction time. This result indicated that, like pkDAO, hDAO can metabolize D-KYN to KYNA (11,12).…”

“…Despite this research focus on DAO inhibition, the primary pharmacological action of most institutionally prescribed antipsychotics is the blockade of dopamine D2 and serotonin receptors (2); however, these drugs might also inhibit DAO activity in vivo. Therefore, an evaluation of the DAO-inhibitory effects of antipsychotics presently prescribed in medical institutions is important because their efficacy might (11,12). Thus, in the present study, this in vitro assay was applied to human DAO (hDAO) and was used to evaluate the DAO-inhibitory effects of currently prescribed antipsychotic drugs, as well as of concomitant drugs prescribed to schizophrenia patients.…”

Fluorimetric assay for D-amino acid oxidase activity in rat brain homogenate by using D-kynurenine as a substrate

“…The pellet was suspended in 150 μL of 0.4 M Tris-buffer (pH 8.3) and subjected to the DAAO assay as an enzyme source. The DAAO assay was carried out according to the previously published method (18,19) with minor modifications.…”

“…The corresponding α-keto acid, 2-oxo-4-(2-aminophenyl)-4-oxobutanoic acid may be instantaneously produced as an intermediate in this reaction, but the α-keto acid appears to be immediately thereafter transformed to KYNA by intramolecular cyclization (18). Thus, the fluorescence intensity of KYNA can be utilized in conjunction with a standard of pig kidney (pk) DAAO in a fluorimetric assay to evaluate several compounds including drugs inhibiting DAAO activity (18,19).…”

“…Here, we measured DAAO activity in the brain tissues of Sprague-Dawley (SD) rats according to our previously described in vitro assay using D-KYN as the substrate (18). The inhibition of the DAAO activity by 2 kinds of commercial DAAO inhibitors, as well as the correlation between DAAO mRNA expression and the enzyme activity was examined to determine the reliability of the proposed DAAO assay.…”