Dehydro-enkephalins [ΔAla2]-, [ΔAla3]-, [ΔPhe4]-, and [ΔLeu5]enkephalins, were examined for their stability to enzymatic hydrolysis by carboxypeptidase Y [EC 22.214.171.124]. The successively liberated amino acids were determined quantitatively by amino acid analyses. The saturated leucine-enkephalin was rapidly hydrolyzed from the COOH-terminus. However, peptide linkages with α,β-dehydroamino acid residues placed in the enkephalin molecule were strongly resistant to the enzyme at the carboxyl side and completely resistant at the amino side of the dehydro residue. © 1982.
Shimohigashi, Y., Chen, H. C., & Stammer, C. H. (1982). The enzyme stability of dehydro-enkephalins. Peptides, 3(6), 985–987. https://doi.org/10.1016/0196-9781(82)90069-9