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

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Abstract
α‐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.