The Outstanding Biological Stability ofβ- andγ-Peptides toward Proteolytic Enzymes: An In Vitro Investigation with Fifteen Peptidases

Abstract

A series of 36 linear and cyclic β- and γ-peptides consisting of as few as two, and as many as 15 residues, was offered as substrates to 15 commercially available proteases of bacterial, fungal, and eukaryotic origin, including a β-lactamase and amidases, as well as most vigorous, nonspecific proteases, such as the 20 S proteasome from human erythrocytes. For comparison, an α-eicosapeptide and standard substrates of the proteolytic enzymes were included in the investigation. Under conditions of complete cleavage of the α-peptide within 15 min the β- and γ-peptides were stable for at least 48 h. Inhibition studies with seven β- and γ-peptides and α-chymotrypsin show that the residual enzyme activity toward succinyl-Ala-Ala-Pro-Phe-p-nitroanilide is unchanged within experimental error after incubation for 15 min with the peptide analogues. Thus, β- and γ-peptides with proteinogenic side chains, that is, consisting of the singly or doubly homologated natural α-amino acids (one or two CH2 groups inserted in the backbone of each residue), are completely stable to common proteases, without inhibiting their normal activity (as demonstrated for α-chymotrypsin). This proteolytic stability of peptides built of homologated amino acids is a prerequisite for their potential use as drugs.