Synthesis of adrenal peptide E and some of its biological activities

A synthesis of peptide E, a highly potent, 25-amino acid adrenal opioid peptide containing both a [Met]enkephalin at the NH2-terminus and [Leu]enkephalin sequence at the COOH-terminus, originally isolated from bovine adrenal medulla [D. L. Kilpatrick, T. Taniguchi, B. N. Jones, A. S. Stern, J. E. Shively, J. Hullihan, S. Kimura, S. Stein, and S. Udenfriend (1981) Proc. Natl. Acad. Sci. USA 78, 3265-3268], is reported. The synthesis was accomplished by the solid-phase method employing the 4-(aminoacyloxymethyl)phenylacetamidomethyl(Pam)-copoly(styrene-1% divinylbenzene) resin. Two synthetic strategies (N-indole formyl protected vs unprotected tryptophan) were followed and results compared and evaluated. It was determined that peptide E prepared with protection of tryptophan (residues 13 and 14) was preferred and gave final product that was readily purified by HPLC. The biological activity of the synthetic material was found to be equivalent to the reported activity of the natural compound.