PUB - Publikationen an der Universität Bielefeld

Cathepsin C is a papain-like cysteine protease with dipeptidyl aminopeptidase activity that is thought to activate various granule-associated serine proteases. Its exopeptidase activity is structurally explained by the so-called exclusion domain, which blocks the active-site cleft beyond the S2 site and, with its Asp1 residue, provides an anchoring point for the N terminus of peptide and protein substrates. Here, the hydrazide of (2S,3S)-trans-epoxysuccinyl-l-leucylamido-3-methylbutane (E-64c) (k(2)/K-i=140 +/- 5 M-1 s(-1)) is demonstrated to be a lead structure for the development of irreversible cathepsin C inhibitors. The distal amino group of the hydrazide moiety addresses the acidic Asp1 residue at the entrance of the S2 pocket by hydrogen bonding while also occupying the flat hydrophobic S1'-S2' area with its leucine-isoamylamide moiety. Furthermore, structure-activity relationship studies revealed that functionalization of this distal amino group with alkyl residues can be used to occupy the conserved hydrophobic S2 pocket. In particular, the n-butyl derivative was identified as the most potent inhibitor of the series (k(2)/K-i=56000 +/- 1700 M-1 s(-1)).