Angliker H Wikstrom P Kirschke H Shaw E 1989 An attempt has been made to extend to the cysteinyl exopeptidases cathepsins H and C affinity-labelling approaches shown to be effective with cysteinyl endopeptidases such as cathepsins B and L and the calcium-activated proteinase. This involved the preparation of amino acid and dipeptide derivatives with unblocked N-termini to satisfy the aminopeptidase and dipeptidyl aminopeptidase characteristics of cathepsins H and C respectively. For covalent reactivity, the possibilities examined included diazomethanes (-CHN2), fluoromethanes (-CH2F) and dimethylsulphonium salt [-CH2S+(CH3)2]. A dipeptidylfluoromethane with a free amino group could not be prepared, perhaps due to inherent instability. Cathepsin H was inactivated by 1 microM-H2N-Phe-CH2F (the 'H2N' indicates a free unblocked amino group) (k2 = 1878 M-1.s-1); this reagent was without effect on cathepsins C and B, even at 100-fold this concentration. Analogous selectivity was shown by H2N-Ser(OBzl)-CHN2 and H2N-Phe-CH2S+(CH3)2, members of other classes of covalently binding reagents. For cathepsin C the dipeptide derivatives H2N-Gly-Phe-CHN2 and H2N-Phe-Ala-CH2S+(CH3)2 caused rapid inactivation near 10(-7) M. Higher concentrations inactivated cathepsins H and B, but the rates were slower by two to three orders of magnitude than for cathepsin C. application/pdf https://sonar.ch/global/documents/92666 eng info:eu-repo/semantics/altIdentifier/doi/10.1042/bj2620063 info:eu-repo/semantics/altIdentifier/pmid/2818577 info:eu-repo/semantics/openAccess The Biochemical journal. - 1989 Affinity Labels Animals Cathepsin B Cathepsin C Cathepsin H Cathepsins Cysteine Endopeptidases Dipeptidyl-Peptidases and Tripeptidyl-Peptidases Dose-Response Relationship, Drug The inactivation of the cysteinyl exopeptidases cathepsin H and C by affinity-labelling reagents. http://purl.org/coar/resource_type/c_6501