β-ENDORPHIN: ISOLATION, AMINO ACID SEQUENCE AND SYNTHESIS OF THE HORMONE FROM HORSE PITUITARY GLANDS

Beta‐endorphin has been isolated from equine pituitaries. Its amino acid sequence is identical to that of ovine, bovine and camel β‐endorphins except for substitution of the threonine residue at position 6 by serine. The equine β‐endorphin has also been synthesized by the solid‐phase method. In comparison with the human hormone, equine β‐endorphin was shown to possess 3 times the receptor‐binding activity in rat membrane preparations and 1.6 times the analgesic potency in the mouse tail‐flick assay.