CHEMBL5731458

Inhibition Assay of Arginase: Inhibition of arginase I (ARG I) and arginase II (ARG II) by Formula I or Formula II compounds is followed spectrophotometrically at 530 nm. The compound to be tested was dissolved in DMSO at an initial concentration 50-fold greater than its final concentration in the cuvette. 10 μl of the stock solution was diluted in 90 μl of the assay buffer that comprises 0.1M sodium phosphate buffer containing 130 mM NaCl, pH 7.4, to which is added ovalbumin (OVA) at a concentration of 1 mg/ml. Solutions of arginase I and II were prepared in 100 mM sodium phosphate buffer, pH 7.4 containing 1 mg/ml of OVA to give an arginase stock solution at a final concentration of 100 ng/ml. To each well of a 96-well microtiter plate was added 40 μl of enzyme, 10 μl of an inventive compound and 10 μl of enzyme substrate (L-arginine+manganese sulfate). For wells that were used as positive controls, only the enzyme and its substrate were added, while wells used as negative controls contained only manganese sulfate. After incubating the microtiter plate at 37° C. for 60 minutes, 150 μl of a urea reagent obtained by combining equal proportions (1:1) of reagents A and B is added to each well of the microtiter plate to stop the reaction. The urea reagent is made just before use by combining Reagent A (10 mM o-phthaldialdehyde, and 0.4% polyoxyethylene (23) lauryl ether (w/v) in 1.8 M sulfuric acid) with Reagent B (1.3 mM primaquine diphosphate, 0.4% polyoxyethylene (23) lauryl ether (w/v), 130 mM boric acid in 3.6 mM sulfuric acid). After quenching the reaction mixture, the microtiter plate is allowed to stand for an additional 10 minutes at room temperature to allow the color to develop. The inhibition of arginase was computed by measuring the optical density (OD) of the reaction mixture at 530 nm and normalizing the OD value to percent inhibition observed in the control. The normalized OD is then used to generate a dose-response curve by plotting the normalized OD values against log [concentration] and using regression analysis to compute the IC50 values.