The ability of bovine brain extracts to compete in a selective fashion for opiate receptor binding is attributable to a small peptide. The substance has been purified to homogeneity and identified as comprising two penta-peptides HTyrGlyGlyPheLeuOH (Leucine-enkephalin) and HTyrGlyGlyPheMetOH (methionine enkephalin). Bovine brain contains 4 times as much leucine-enkephalin as methionine-enkephalin in contrast to pig brain in which these ratios are reversed. Competition for opiate receptor binding by leucine-enkephalin is reduced more by sodium and enhanced more by manganese than is the case for methionine-enkephalin, suggesting that leucine-enkephalin may be a "purer" agonist than methionine-enkephalin.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)