Cathepsin B is a lysosomal cysteine protease. It is implicated in playing a role in protein degradation, arthritis, apoptosis, and cancer. Biovision’s Procathepsin B can be auto-catalytically activated to mature Cathepsin B (~28 kDa) by adding an equal volume of 0.2 M NaOAc, 5 mM EDTA pH 4.0 containing fresh 5 mM DTT at room temperature (RT). The enzyme is fully activated within 3-4 h of incubation at RT. After activation mature Cathepsin B is highly auto-proteolytic at pH 4.0, and care must be taken to avoid self-proteolysis. If the activated enzyme is not used immediately, methylmethanthiosulfonate (1 mM final concentration; MeS-SO2Me; MMTS) could be added and sample should be frozen at -80°C. The activity can be then restored by adding L-cysteine (3 M excess over MMTS) to the enzyme solution.
