Peptide p-nitrophenylanilides containing (E)-dehydrophenylalanine—synthesis, structural studies and evaluation of their activity towards cathepsin C

Tetrapeptide p-nitroanilides containing (E)-dehydrophenylalanine were synthesized and evaluated as inhibitors and substrates of cathepsin C. Peptides containing a free, unblocked amino group appeared to be quite good substrates of the enzyme, whereas fully protected peptides acted as very weak inhibitors. Structural studies by means of NMR and CD, alongside with molecular modelling, have proved that these peptides are hydrolysed in one step by direct removal of p-nitroaniline from the tetrapeptide.