Mass spectrometric and biological characterization of guinea-pig corticotrophin.
Guinea-pig ACTH has been found to be distinct from other mammalian ACTHs in having an alanine for proline substitution at position 24 and in having superagonist aldosterone-stimulating activity relative to synthetic ACTH(1-24) in an isolated rat glomerulosa cell bioassay. We have purified ACTH from extracts of guinea-pig anterior pituitary and confirmed its unusual structural characteristics by amino acid analysis and mass spectrometry. Using isolated rat adrenal fasciculata-reticularis and glomerulosa cell bioassays, guinea pig ACTH was found to have similar activity to that of human ACTH with respect to corticosterone- and aldosterone-stimulating activity, in terms of maximal steroid output but was slightly more potent in terms of the concentration which elicited half-maximal steroid secretion. Under the assay conditions used, guinea-pig ACTH appeared not to be a superagonist as previously suggested. Various biosynthetic derivatives of guinea-pig pro-opiomelanocortin were identified by amino acid analysis and mass spectrometry. Joining peptide, a major product of pro-opiomelanocortin processing, was found in extracts of both anterior and neurointermediate lobes of the pituitary. Post-translational modification of other products of intermediate lobe processing were observed. N- and O-acetylation of alpha-melanotropin, partial O-phosphorylation of corticotropin-like intermediate lobe peptide and carboxyl-terminal amidation of beta-melanotropin were identified.
Robinson
P
P
Royal Victoria Hospital, Department of Medicine, McGill University, Montreal, Quebec, Canada.
Toney
K
K
James
S
S
Bennett
H P
HP
D000324:Adrenocorticotropic Hormone / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D000450:Aldosterone / Q000096:biosynthesis; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001681:Biological Assay; D003345:Corticosterone / Q000096:biosynthesis; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000737:chemistry / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D015384:Zona Glomerulosa / Q000187:drug effects / Q000378:metabolism
D000596:Amino Acids; D000450:Aldosterone; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone