The specificity of bovine spleen cathepsin S. A comparison with rat liver cathepsins L and B.
The peptide-bond-specificity of bovine spleen cathepsin S in the cleavage of the oxidized insulin B-chain and peptide methylcoumarylamide substrates was investigated and the results are compared with those obtained with rat liver cathepsins L and B. Major cleavage sites in the oxidized insulin B-chain generated by cathepsin S are the bonds Glu13-Ala14, Leu17-Val18 and Phe23-Tyr26; minor cleavage sites are the bonds Asn3-Gln4, Ser9-His10 and Leu15-Tyr16. The bond-specificity of this proteinase is in part similar to the specificities of cathepsin L and cathepsin N. Larger differences are discernible in the reaction with synthetic peptide substrates. Cathepsin S prefers smaller neutral amino acid residues in the subsites S2 and S3, whereas cathepsin L efficiently hydrolyses substrates with bulky hydrophobic residues in the P2 and P3 positions. The results obtained from inhibitor studies differ somewhat from those based on substrates. Z-Phe-Ala-CH2F (where Z- represents benzyloxycarbonyl-) is a very potent time-dependent inhibitor for cathepsin S, and inhibits this proteinase 30 times more efficiently than it does cathepsin L and about 300 times better than it does cathepsin B. By contrast, the peptidylmethanes Z-Val-Phe-CH3 and Z-Phe-Lys(Z)-CH3 inhibit competitively both cathepsin S and cathepsin L in the micromolar range.
Brömme
D
D
Institute of Biochemistry, Medical Faculty, Martin-Luther University, Halle, Saale, German Democratic Republic.
Steinert
A
A
Friebe
S
S
Fittkau
S
S
Wiederanders
B
B
Kirschke
H
H
D000595:Amino Acid Sequence; D000818:Animals; D002401:Cathepsin B / Q000378:metabolism*; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D002417:Cattle; D003546:Cysteine Endopeptidases; D010450:Endopeptidases; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D051381:Rats; D013154:Spleen / Q000201:enzymology*; D013379:Substrate Specificity
D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L; C534280:Ctsl protein, rat; C028217:cathepsin S