Fig. 3.

Specificity profiles of SARS-CoV PLpro, USP5 and UCH-L3 against fluorogenic AMC derivatives of Ubl and variants. The catalytic efficiency (k_cat/K_M) against the AMC substrates is plotted on a log scale. All reactions were carried out at pH 7.8, in presence of 2 mM DTT, 2% DMSO, and at 25 °C. For USP5 enzyme assays, 100 nM of free ubiquitin was also included. The substrates used are ISG15-AMC (black), Ub-AMC (gray), Nedd8-AMC (white), ISG15(C)-AMC (horizontal lines) and ISG15(N)-Ub-AMC (crosshair).