Purification and characterization of cathepsin S from hepatopancreas of carp Cyprinus carpio

Cathepsin S was purified from carp hepatopancreas to homogeneity up to 300- fold. The amino acid sequence of its NH2-terminus was determined to be V-P- D-A-M-D-W-Y-N-K-G-Y-V-T-D-V-K-N-Q. On the contrary, that of purified cathep sin L from carp hepatopancreas was to be V-P-N-S-L-D-W-R-E-K-G. Purified ca thepsin S consisted of a single chain with 37 kDa estimated by sodium dodec ylsulfate-polyacrylamide gel electrophoresis. The enzyme had strong hydroly tic activity toward Z-Phe-Arg-MCA with the pH optimum of 7.0, but this lack ed the ability to hydrolyze most of the other MCA substrates. The optimum p H of cathepsin S for protein substrate (carp myosin heavy chain) was also t o be pH 7.0. These properties of purified cathepsin S obviously differ from cathepsins B and L. The enzyme activity was totally inhibited by E-64, leu peptin, 5-5'-dithiobis (2-nitro-benzoic acid) and p-tosyl-lys chloromethylk etone as well.