CHEMBL5738525

S-Tetralol Oxidation Assay: the inhibitory potency of the individual compounds against the AKR1C isoforms was determined by monitoring the NADP+ dependent oxidation of S-tetralol catalyzed by the AKR1C enzymes using substrate concentrations at their Km values in the presence and absence of varying concentration of the inhibitors (Adeniji, et al., 2012, J Med Chem 55:2311-2323). Reaction systems (200 μL) contained 100 mM potassium phosphate buffer (pH 7.0), 4% DMSO, 200 μM NADP+, a serial dilution of compounds, S-tetralol, and AKR1C enzymes. The concentration of S-tetralol used in the inhibition assays using AKR1C1, 1C2, 1C3, and 1C4 was 5, 22.5, 165, and 25 μM, respectively, which was equal to their Km values in order to make a direct comparison of IC50 values. The concentration of AKR1C1, 1C2, 1C3, and 1C4 was 111, 86, 95, and 552 nM, respectively. Reagents were mixed and incubated at 37° C. for 10 min followed by adding AKR1C enzymes to initiate the reaction. A continuous fluorometric assay (Ex, 340 nm; Em, 460 mM) to measure NADPH formation was conducted at 37° C. for 5 min, and the IC50 value of each compound was calculated. To determine the pattern of inhibition, five fixed concentrations of S-tetralol were used and four different concentrations of inhibitor were used and a gobal fit of the equations for COMP, NONCOMP and UNCOMP to the data was applied using Grafit.