Fig. 6.

Effect of proteinase inhibitors on proteolytic activity. The 3CLpro (5 μM) in 50 mM Tris/HCl buffer (pH 7.5) containing 100 mM NaCl was preincubated with different proteinase inhibitors (5 mM final concentration) for 2 h at 8°C. Thereafter, the substrate (5 μM final concentration) was added, and the extent of cleavage was calculated after 24 h incubation at 8°C. The cleavage activity in the absence of inhibitors was defined as 100%. Lane C, reaction without proteinase inhibitors. Lanes 1 through 7, reactions with antipain, PMSF, leupetin, TPCK, benzamidine, E-64 and EDTA