CHEMBL5735146

Proteasome-Activity Inhibitory Assay: Inhibition of the chymotrypsin-like (CT-L), peptidylglutamyl peptide hydrolyzing activity (PGPH), and trypsin-like (T-L) activities of the 20S proteasome in enzymatic assays were determined using succinyl-Leu-Leu-Val-Tyr-AMC (10 μmol/L), Z-Leu-Leu-Glu-AMC (10 μmol/L) and Boc-Leu-Arg-Arg-AMC (50 μmol/L), respectively, as the substrates with purified human 20S proteasome at 2, 4 and 8 nmol/L, respectively, in the assay buffer containing 25 mM HEPES (pH7.5), 0.5 mM EDTA, 0.002% sodium dodecyl sulfate (SDS) and 0.05% NP-40. Stock solutions of the 20S proteasome inhibitors disclosed herein were prepared in dimethyl sulfoxide (DMSO) and the final DMSO concentration in the assay mixture was 1%. Reaction was conducted at room temperature for one hour. Proteasome activity was measured based on detection of the fluorophore 7-Amino-4-methylcoumarin (AMC) after cleavage from the substrates with a plate-based spectrofluorometer. IC50 is a quantitative measure indicating the concentration of an inhibitor at which the catalytic activity of the 20S proteasome is inhibited by 50%.