Fig. 7.
Inhibition of the SARS-CoV-2 PLpro protease activity by small molecules. To investigate in vitro inhibition of protease activity a PLpro enzymatic inhibition assay measuring protease activity was performed. Using a proprietary fluorogenic substrate (BPS Bioscience), fluorescence intensities at an emission wavelength of 460 nm were measured. The small molecules rutin (closed circles), and cyanidin-3-0-glucoside (open circles) were shown to result in a concentration-dependent inhibition of protease activity (A). The concentration range between 3 μM and 200 μM was investigated. Average values ± SEM from triplicate determinations are depicted. The average background (n = 3), total protease activity (n = 6), and inhibition by the noncovalent positive control GRL-0617 at 100 μM (n = 3), are highlighted (horizontal dotted lines). The % inhibition of PLpro protease activity at 100 μM concentrations of the indicated small molecule inhibitors was calculated (B). Average values ± SEM from triplicate determinations are depicted.