Synthesis and evaluation of new elastase substrates as tripartate prodrugs

Compounds consisting of a peptide sequence, 4-aminobutyric acid or 5-aminovaleric acid, respectively, as spacer units, and benzyl alcohol as a model leaving group have been prepared and tested for their ability to serve as substrates for porcine pancreatic elastase and human polymorphnuclear elastase. Those compounds containing an Ala-Ala-Ala sequence served as effective substrates for both enzymes. Hydrolytic cleavage, however, occurred exclusively at the ester bond, not at the peptide-spacer bond. In order to direct the cleavage site from the ester to the amide bond the peptide sequence was varied. We introduced a proline residue in P(3) (in relation to the ester bond) which is known to prevent the cleavage of a substrate by elastase. No hydrolysis, however, either of the ester bond or of the peptide-spacer bond, was found for these compounds.