Biosynthesis of Pairs of Peptides Related to Melanotropin, Corticotropin and Endorphin in the Pars Intermedia of the Amphibian Pituitary Gland

摘要: This study concerns the biosynthesis of a number peptides in neurointermediate lobe pituitary gland aquatic toad, Xenopus laevis. Using pulse-chase incubations vitro and high-performknce liquid chromatographic analysis, it could be shown that these are synthesized through processing pro-hormone, pro-opiomelanocortin; all were released into incubation medium. On basis electro-phoretic selective amino acid incorporation immunoprecipitation, as well peptide mapping by high-performance chromatography, classified three distinct groups: two related to melanocyte-stimulating hormone (melanotropin), adrenocorticotropic (corticotropin) endorphin-like peptides. tryptic chymotryptic maps synthetic α-melanotropin des-AcαN-α-melanotropin references, one melanotropin-like was identified des-AcαN-α-melanotropin; other represents neither nor any known melanotropic peptide. The immunologically corticotropin had characteristics consistent with structures resembling previously named ‘corticotropin-like intermediate peptide’, corticotropin-(18-39). endor-phin-like peptides, although highly related, do not have same primary structure. In view apparent structural differences between each group, possible occurrence prohormones is discussed.