Unknown

Appropriate amounts (0.23−4.2 μg) of the purified D-aspartate oxidase was added to a reaction mixture of air-saturated 40 mM sodium pyrophosphate buffer (pH 8.3), 23 U A. niger catalase, 60 μM FAD, and 10 mM amino acids in a final volume of 150 μL. For testing the inhibitory activity of mesotartaric acid, mesotartaric acid was added to the reaction mixture. The mixture was incubated at 37 °C for 10 min, and then 10 μL of 100% (weight/vol) trichloroacetic acid was added to stop the reaction. The 2-oxo acid product was reacted with 2,4-dinitrophenylhydrazine and quantitated by measuring the A445 against a blank mixture lacking amino acids.