Differences in the post-translational processing of beta-endorphin in rat anterior and intermediate pituitary

The immunoactive beta-endorphin-related material in extracts of rat anterior and intermediate/posterior pituitary was separated by ion exchange chromatography on sulfopropyl-Sephadex (Zakarian, S., and Smyth, D. G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 5972-5976). The profile of beta-endorphin immunoactivity in rat anterior pituitary was distinctly different from that found in intermediate/posterior pituitary. In the rat anterior pituitary, most of the immunoactivity co-migrated with synthetic camel beta-endorphin(1-31); in the intermediate/posterior pituitary, only about 10% of the immunoactivity co-migrated with camel beta-endorphin(1-31). In rat anterior pituitary cell suspensions incubated with [3H]tyrosine for 6 h or 48 h, material co-migrating with camel beta-endorphin(1-31) was the major final posttranslational product related to beta-endorphin. This material was reanalyzed by chromatography on sulfopropyl-Sephadex, analyzed by gel filtration on Sephadex G-50 in 6 M guanidine HCl, and digested with pronase and trypsin. In every analysis, the major peak of [3H]tyrosine-labeled anterior pituitary beta-endorphin was indistinguishable from camel beta-endorphin(1-31).