Control of cell protein degradation. Changes in activities of lysosomal proteases.

In cycloheximide-treated fibroblasts, the rate of cell proteolysis and the specific activity of cathepsin D show a rapid, concurrent, and proportional decrease over a 48 h period. Cathepsin B1 also decreases, but other lysosomal enzymes show litte or no change in specific activity. These findings are consistent with the hypothesis that the rate of proteolysis in the cell is in part controlled by the specific activities of lysosomal proteases.