title: Degradation of deltorphins and their analogs by rat brain synaptosomal peptidases.
abstract: To obtain metabolically stable peptide ligands with high affinity and selectivity for the delta-opioid receptor, the enzymatic stability of deltorphins and their analogs was examined by using a crude rat brain synaptosomal membrane fraction. It was found that deltorphin (DLT: Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2) was easily degraded, producing DLT (1-4) and DLT (1-5) as the major degradation products, whereas [D-Ala2]deltorphin II (DL-II: Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2) was very stable. Experiments with some enzyme inhibitors strongly suggested that the degradation of DLT was initiated by cleavage of the Leu5-Met6 bond by a metalloendopeptidase. On the other hand, stability experiments on DL-II analogs demonstrated that the presence of amino acids branched at the beta-carbon atom or with a bulky side chain as residue 5 is of importance for the enzymatic stability. Based on these lines of evidence, some enzyme-resistant DLT analogs were synthesized.
authors.affiliation: Tohoku College of Pharmacy, Sendai, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Sasaki
authors.forename: T
authors.initials: T
authors.lastname: Chiba
authors.forename: A
authors.initials: A
authors.lastname: Ambo
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D010450:Endopeptidases / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*
chemical_list: D009842:Oligopeptides; D011480:Protease Inhibitors; C059567:deltorphin; D010450:Endopeptidases