A series of D-amino acid-substituted analogs of the opiate peptide, methionine5-enkephalin, were synthesized by solid-phase methods and tested for their abilities to inhibit electrically-evoked contractions of mouse vasa deferentia and to compete with tritiated enkephalin for opiate receptors on particulate fractions isolated from homogenates of rat brain. [D-Ala2]-enkephalin and [D-Ala2]-enkephalin amide were found to be the most potent peptides in both assay systems, being about 1000% active in the vas deferens bioassay and 120% and 150% active, respectively, in the stereospecific binding test relative to methionine5-enkephalin itself. In comparison, [D-Met5]-, [D-Tyr1]-, [D-Leu2]-, [D-Phe2]-, [D-Ala3]-, and [D-Phe4]-enkephalin had not more than 10% activity. The stabilization of the β-bend conformation of methionine5-enkephalin by the substitution of D-alanine in position 2 of the peptide chain may contribute to the high activities of the [D-Ala2]-analogs.
|Number of pages||7|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Dec 6 1976|
ASJC Scopus subject areas
- Molecular Biology