Isolation of the opioid heptapeptide Met-enkephalin [Arg6,Phe7] from bovine adrenal medullary granules and striatum.

Abstract
Bovine adrenal chromaffin granules contain, in addition to Met-enkephalin and Leu-enkephalin, at least 3 small peptides with opiate receptor activity. One of the these adrenal peptides was purified to homogeneity and its sequence was shown to be Met-enkephalin-[Arg6,Phe7]. This heptapeptide was also found in beef striatal extracts in amounts comparable to those of Leu-enkephalin.