Figure 6. Characterization of extralysosomal proteolytic activity. The results indicates a marked effect of siramesine on both the proteasome and calpain proteolytic systems. Reduction of proteolytic activity in human lens epithelial cells (HLEC) incubated with 30 µM siramesine (100 percent on the y-axis) after addition of calpeptin (Cal) or lactacystin (Lact). Proteolysis was measured with the synthetic peptide substrate LLVY, which can be cleaved both by the proteasome and by calpain. Formation of the cleavage product was measured continuously and the effects of the proteasome inhibitor lactacystin and the calpain-inhibitior calpeptin are shown relative to that of the proteolytic activity in cells exposed to 30 µM siramesine without inhibitor. The experiment was repeated three times. n=16. Mean±SEM is shown. p<0.001 (***).