Electrospray mass spectrometric techniques were used to demonstrate that mature (single-chain) recombinant rat cathepsin B is capable of sequentially removing the three dipeptides which comprise the C-terminal extension of the proenzyme. A pepsin-cleaved form of a non-active mutant recombinant rat procathepsin B (Cys-29-Ser) was used as a ‘substrate’ to study C-terminal processing by mature cathepsin B. The results indicate that the first two residues (Arg-Phe) are removed efficiently, while the remaining four (Gln-Tyr-Trp-Gly), particularly the final two, are much more resistant to proteolysis. These cleavages were pronounced at pH 5.0 compared with pH 6.0, in agreement with the lower pH optimum for cathepsin B exopeptidase activity reported previously. From this example of the peptidyldipeptidase activity of cathepsin B we conclude that removal of the C-terminal extension may occur in any intracellular compartment where active cathepsin B is found.
Demonstration by electrospray mass spectrometry that the peptidyldipeptidase activity of cathepsin B is capable of rat cathepsin B C-terminal processing
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A D Rowan, R Feng, Y Konishi, J S Mort; Demonstration by electrospray mass spectrometry that the peptidyldipeptidase activity of cathepsin B is capable of rat cathepsin B C-terminal processing. Biochem J 15 September 1993; 294 (3): 923–927. doi: https://doi.org/10.1042/bj2940923
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