Open AccessPrimary structures of three fragments of proglucagon from the pancreatic islets of the daddy Sculpin ( Cottus scorpius )
Author(s) -
CONLON J. Michael,
FALKMER Sture,
THIM Lars
Publication year - 1987
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1987.tb11001.x
Subject(s) - proglucagon , glucagon , biology , peptide , carboxypeptidase , protein primary structure , selenocysteine , stereochemistry , chemistry , biochemistry , peptide sequence , enzyme , glucagon like peptide 1 , endocrinology , cysteine , gene , hormone , type 2 diabetes , diabetes mellitus
Three peptides isolated from the Brockmann bodies of the daddy sculpin, a teleostean fish, have been identified as fragments of one or more proglucagons. The peptide L Q D A E D S S R F D A D D T L A G E A R E L S T P K represents the NH 2 terminus of proglucagon (residues 1–27), H S E G T F S N D Y S K Y L E T R R A Q D F V Q W L K N S represents glucagon and H A D G T F T S D V S S Y L N D Q A I K D F V A K L K S G K V represents the glucagon‐like peptide at the COOH terminus of the precursor. The fast‐atom bombardment mass spectra of the three peptides were consistent with the proposed structures and demonstrated that further posttranslational modifications of the peptides had not taken place. Sculpin glucagon is identical to anglerfish glucagon II but sculpin proglucagon (1–27) and glucagon‐like peptide show stronger homology to the corresponding regions of anglerfish proglucagon I than to proglucagon II. The structures of the peptides are suggestive of the action of trypsin‐like and carboxypeptidase‐B‐like enzymes at the site of pairs of basic amino acid residues in proglucagon. The presence of a COOH‐terminal lysyl group in proglucagon(1–27) may indicate, however, that the penultimate prolyl residue partially inhibits the action of the carboxypeptidase‐B‐like activity.