Figure 3.

The effect of reaction pH on peptidase activities. Assays were carried out in a 200 μl reaction mixture containing 50 mM HEPES-Tris at pH 6.2–9.8, 1 μg/ml 20S proteasome, and 10 μM of peptidyl substrates (A: Suc-LLVY-MCA for chymotrypsin-like activity; B: Z-LLE-MCA for PGPH activity; C: Boc-LRR-MCA for trypsin-like activity) at 37°C for 1 h. Reactions were started and stopped as described in methods. Symbols represent the wild-type strain (○) and the rpt6-1 mutant (●). Values are means ± SD for three independent experiments.