N-Hydroxy peptides as substrates for α-chymotrypsin

An N-hydroxylated peptide bond was found to be cleaved faster by an endopeptidase than the corresponding peptide band. This preferred enzymatic cleavage was detected during proteolytic studies of the N-hydroxy peptide SIINF psi[CO-N(OH)]GKL in the presence-of the serine protease chymotrypsin in comparison with the natural SIINFEKL epitope and related analogs. For the first time, the replacement of the peptide bond by another motif afforded an oligomer which is degraded faster than the natural peptide. The N-hydroxy peptide is also more sensitive to the enzymatic degradation than the Gly-containing analog SIINFGKL. A tentative explanation for the unexpected higher cleavage rate of the CO-N(OH) bond is given on the basis of the N-OH intramolecular H-bonding capacity as indicated by NMR experiments. This property of the hydroxamate group may be of a particular advantage for the introduction of a specific cleavage site within peptidomimetics or in prodrugs.