Demonstration by electrospray mass spectrometry that the peptidyldipeptidase activity of cathepsin B is capable of rat cathepsin B C-terminal processing.
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.
Joint Diseases Laboratory, Shriners Hospital for Crippled Children, Montreal, Quebec, Canada.
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AD
Rowan
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R
Feng
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Y
Konishi
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JS
Mort
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002401:Cathepsin B / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010434:Pepsin A / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D013379:Substrate Specificity
D004792:Enzyme Precursors; D009838:Oligodeoxyribonucleotides; D010450:Endopeptidases; D002401:Cathepsin B; D010434:Pepsin A