Isolation and characterization of α-endorphin and γ-endorphin from single human pituitary glands

Abstractα-endorphin and γ-endorphin, two closely related peptides of the pro-opiomelanocortin family with characteristics biological activities, were purified to homogeneity from single human pituitary glands and chemically identified. Isolation of the peptides was based on size fractionation by Sephadex G-75 chromatography followed by two HPLC steps using reverse-phase and paired-ion reverse-phase systems and was monitored by radioimmunoassay. During the isolation procedure α-and γ-endorphin-sized material behaved chromatographically and immunologically indistinguishably from synthetic α- and γ- endorphin. The amino acid composition and NH2-terminus of isolated peptides demonstrated their identity as authentic α-endorphin and γ-endorphin. Acetylated forms were absent. In addition, evidence is provided that large forms with α- and γ-endorphin immunoreactivity detected during gel filtration are human lipotropin-(1–74) and -(1–75), respectively. The data substantiate that α-endorphin and γ-endorphin exist as endogenous peptides in the human pituitary gland