alpha-Melanocyte-stimulating-hormone precursors in the pig pituitary.
The occurrence of intermediates from the processing of ACTH-(1-39) [adrenocorticotropic hormone-(1-39)] to alpha-melanocyte-stimulating hormone was investigated in normal pig pituitaries by the use of sensitive and specific radioimmunoassays for ACTH-(1-13), ACTH-(1-14), ACTH-(1-13)-NH2 and ACTH-(1-39). Fractionation by reverse-phase h.p.l.c. revealed ACTH(1-17) and their acetylated analogues. The intermediate lobe contained NO-diacetyl-ACTH-(1-13)-NH2, N-acetyl-ACTH-(1-13)-NH2 and ACTH-(1-13)-NH2. In addition, the corresponding ACTH-(1-14) peptides (the glycine-extended precursor of the amidated peptides) were detected in lower amounts in both the intermediate lobe and the anterior lobe. ACTH-(1-17), ACTH-(1-13) and their acetylated analogues could not be detected in the anterior lobe or the intermediate lobe. The results suggest that an endopeptidase initially cleaves ACTH-(1-39) at the Lys-16-Arg-17 bond. ACTH-(1-16) is then processed by a pituitary carboxypeptidase to ACTH-(1-14) and ACTH-(17-39) by the aminopeptidase to ACTH-(18-39).
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D011863:Radioimmunoassay; D012974:Sodium Iodide; D013552:Swine; D000521:alpha-MSH / Q000031:analogs & derivatives*
D010446:Peptide Fragments; C038513:ACTH (1-14); D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D012974:Sodium Iodide; C028238:ACTH (1-17)