Biological and Pharmacokinetic Studies with ?-Peptides

Interactions and cleavage reactions of ?-amino acids and ?-oligopeptides (up to nine residues, carrying the side chains of Ala, Val, Leu, Ile, Phe, Ser, Lys, and Hop) with biological systems, such as the most potent peptidases (pronase, proteinase K, 20S proteasome), microorganisms (Pseudomonas aeruginosa and Pseudomonas putida), and mammalian blood (intravenous application to rats) have been investigated and compared with ?-peptides. The results are: i) the three peptidases do not cleave ?-peptides at all (within 24 h), and they are not inhibited by a ?-peptide; ii) except for certain 3-aminobutanoic-acid (?-HAla) derivatives, neither free, nor N-acetyl-?-amino acids, nor ?-peptides (offered as sole N and C source) lead to growth of the two bacteria tested; iii) two water-soluble ?-heptapeptides (with Lys side chains) were shown to have elimination half-lives t1/2(?) of 3 and 10 h at 100- and 30-ng/ml levels, respectively, in the rodent blood – much larger than those of ?-peptides. Thus, the preliminary results described here confirm the much greater stability of ?-peptides, as compared to ?-peptides, towards metabolization processes, but they also suggest that there may be interactions (by hitherto unknown mechanisms) between the worlds of ?- and ?-peptides.