| Assay Method Information | |
| | DAAO Enzymatic Assay |
| Description: | The DAAO enzymatic activity assay was modified according to the report of Oguri et al (Oguri, S., Screening of d-amino acid oxidase inhibitor by a new multi-assay method. Food chemistry 2007, 100 (2), 616). The DAAO activity was measured by using substrate D-alanine reaction produced hydrogen peroxide (H2O2) to further react with 3-(4-hydroxyphenyl) propionic acid (HPPA). The HPPA were oxidized by H2O2 and peroxidase to become the fluorogenic dimer which was measured to represent the activity of DAAO. The substrate of DAAO was prepared in 50 mM D-alanine (dissolved in 0.2 M Tris-HCl buffer, pH 8.3). A 100 ul of D-alanine solution was mixed with 4 ul (in 100%) dimethyl sulfoxide, DMSO) of different concentrations of drugs ranging from 31.36 nM, 94.08 nM, 0.28 uM, 0.85 uM, 2.54 uM, 7.62 uM, 22.86 uM, 68.59 uM, 0.21 mM, 0.62 mM, 1.85 mM, 5.56 mM, 16.67 mM, and 50.00 mM with a final DMSO concentrations of 0.167% in each reaction concentration. A 10 ul of D-alanine and drug mixture was incubated with 220 ul of Reaction Master Mix in black 96 well plate at 37° C. for 5 min. The Reaction Master Mix contained 110 ul of 5 U/mL porcine kidney DAAO (Sigma-Aldrich, USA) solution (dissolved with 0.2 M Tris-HCl buffer, pH 8.3), 1.1 mL of 15 U/mL peroxidase solution (dissolved with 0.2 M Tris-HCl buffer, pH 8.3), 1.1 mL of 20 mM HPPA solution (dissolved with 0.2 M Tris-HCl buffer, pH 8.3), and 2.2 ml of 2 M Tris-HCl buffer (pH 8.3) for 110 reaction assays.Fluorescence intensity (Fs) was measured at 405 nm by irradiation excitation at 320 nm. The higher is the DAAO enzymatic activity, the higher is the fluorescence intensity. The fluorometric inhibition indicator (Fi) was obtained from the following equation: Fi=(Fs−FDrug)/(FDMSO). Where the fluorescent drug blank (FDrug) were measured in the drug mixture solution (using 0.2 M Tris HCl buffer, pH 8.3, without D-alanine). A DMSO blank (FDMSO) was measured under a 100% DMSO solution. Although, in the assay for D-amino acid oxidase, FAD was generally included in the reaction mixture because this co-factor is easily dissociated from the holoenzyme, the present method was performed without FAD. The inhibitory effect of DAAO inhibitors was compared by using inhibitory concentrations which reduce 50% of DAAO activity (IC50). The IC50 value was calculated by GraphPad Prism, version 5 software (GraphPad Software, Inc., La Jolla, Calif.) (GraphPad Prism 5, GraphPad software Inc: California, USA) through nonlinear regression model. |
| Affinity data for this assay | |
|---|---|
| If you find an error in this entry please send us an E-mail | |