Peptides including HisGlyTrpSerTyrGlyGlyPheLeu; LeuAspGluAsnValHisPhePhe; GluArgHisSerIleArg and PheValIleGlnGluGluPhe which show peptidase ability and have substrate specificity for at least one of the compounds H-Ala-Pro-pNA, H-Gly-Pro-pNA and H-Arg-Pro-pNA are disclosed. Nucleic acids, vectors, antibodies and hybridoma cells are also claimed with reference to the above sequences and their abilities.