Isolation and characterization of beta-endorphin-like peptides from bovine brains

Four β -endorphin-like peptides from bovine brain extracts have been identified by their behavior in CM-cellulose chromatography, gel filtration, high-performance liquid chromatography, and radioimmunoassay. Two of them have been isolated in sufficient quantity for amino acid analysis, radioimmunoassay, and radioreceptor assay. One peptide has an amino acid composition nearly identical to that of β -endorphin with 56% of the radioimmunoreactivity and 2.3% of the potency in the radioreceptor assay of β -endorphin. The amino acid content of the other β -endorphin-like peptide is very different from that of bovine β -endorphin but it has 47% of the radioimmunoreactivity and 1% of the potency in the radioreceptor assay of β -endorphin.