A. Inhibition of chymotrypsin-like activity. Jurkat cells were treated with 100 nM of each analog for 1 h. The fluorescent substrate suc-LLVY-amc was used to measure CT-L activity. Control cells (treated with DMSO) were normalized to represent 100% activity and cells treated with analogs were compared to control. Shown is the percent of chymotrypsin-like activity observed for each sample for three independent experiments. P values were determined by one way ANOVA and the Bonferroni post-hoc test. B. CT-L activity is recovered over time by non-LG analogs and sustained with LG analogs. Enzymatic activity was analyzed after harvesting cells treated with analogs for 1, 6, 12 and 16 h. C. Level of β5 protein is not decreased after treatment with the LG analog marizomib or the non-LG analog NPI-2078. Jurkat cells treated with 100 nM marizomib or 100 nM NPI-2078 for 1, 6, and 12 h were probed for the chymotryptic-like catalytic subunit, β5. Densitometry is the β5 value normalized to actin.