Opioid hexapeptides and heptapeptides in adrenal medulla and brain possible implications on the biosynthesis of enkephalins

Abstract

Bovine adrenal chromaffin granules have been shown to contain [Met]enkephalin and [Leu]enkephalin and at least seven other small peptides that exhibit specific binding to opiate receptors. Six of these peptides have been characterized and their structures established as ( O)-[Met]enkephalin, [Met]enkephalin-Arg 6-Arg 7, [Met]enkephalin-Lys 6, [Met]enkephalin-Arg 6, [Leu]enkephalin-Arg 6, and [Met]enkephalin-Arg 6-Phe 7. Many of these hexa- and heptapeptides are also present in bovine and human brain. It is suggested that the presence of these peptides in a tissue is evidence of a common biosynthetic pathway of the enkephalins from a large precursor protein.