A 24 amino acid polypeptide that does not originate from (pre)proenkephalin has been isolated from ovine adrenal chromaffin granules. Its sequence is: Arg-Leu-Pro-Gly-Glu-Leu-Arg-Asn-Tyr-Leu-Asp-Tyr-Gly-Glu-Glu-Val-Gly-Glu-Glu-Ala-Ala-Arg-Gly-Val. This peptide is generated from a precursor molecule that has also been purified and partially sequenced. The proteolytic cleavage occurs at a triple Arg site. A search of the available protein sequence data banks shows very little homology to any known protein.