Isolation and primary structure of endorphin from salmon pituitary glands.

Endorphin has been isolated from an acid acetone extract of the pituitary of the salmon $\text{Oncorhynchus}\text{keta}$ by ion exchange chromatography and gel filtration. Sequence analysis revealed it to be a nonacosapeptide with following primary structure: Ac-Tyr-Gly-Gly-Phe-Met-Lys-Pro-Tyr-Thr-Lys-Gln-Ser-His-Lys-Pro-Leu-Ile-Thr-Leu-Leu-Lys-His- Ile-Thr-Leu-Lys-Asn-Glu-Gln-OH. It appears that the amino terminal segment which is necessary for analgesic activity is conserved through the evolution of vertebrate except for the blocking of the amino terminal of salmon endorphin.