Opioid activity of a peptide, beta-lipotropin-(61-91), derived from beta-lipotropin

The pituitary peptide beta-lipotropin displays essentially no opoid activity in a preparation of guinea pig ileum or in the opiate receptor binding assay. However, a fragment, beta-lipotropin-(61-91), with the enkephalin sequence (Tyr-Gly-Gly-Phe-Met) at its NH2-terminus, has typical opioid effects in these two assays.