Biosynthesis of beta-endorphin from beta-lipotropin and a larger molecular weight precursor in rat pars intermedia.
When isolated rat pars intermedia cells were incubated for 10 min with radioactive amino acids, one major labeled protein with a molecular weight of 30,000 +/- 1500 was extracted. This protein was shown to contain in its sequence the antigenic determinants for corticotropin and beta-melanotropin by immunoprecipitation. When the radioactivity incorporated into this large molecular weight protein during the first 10 min was chased by a further incubation in presence of an excess of unlabeled amino acid, the initial protein was degraded into several smaller peptides including beta-endorphin and beta-lipotropin. Another 18,000-dalton peptide was also observed and was tentatively identified as a large molecular form of corticotropin. From the kinetics of the maturation of the initial precursor, it is concluded that the initial cleavage of the 30,000-dalton peptide gives rise to beta-lipotropin and the 18,000-dalton form of corticotropin. beta-Lipotropin is subsequently cleaved to form beta-endorphin.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D004589:Electrophoresis, Disc; D004723:Endorphins / Q000096:biosynthesis*; D066298:In Vitro Techniques; D010455:Peptides / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D008083:beta-Lipotropin / Q000378:metabolism*
D000596:Amino Acids; D004723:Endorphins; D010455:Peptides; D011498:Protein Precursors; D000324:Adrenocorticotropic Hormone; D008083:beta-Lipotropin