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Thyroid Hormones and Calcium Metabolism
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
PTH, a polypeptide containing 84 amino acid residues, is secreted by the chief cells of the parathyroid gland. It is formed in the ribosome as a preprohormone (110 amino acids), which is split into the prohormone (90 amino acids) and then into the hormone in the endoplasmic reticulum and the Golgi apparatus.
Summation of Basic Endocrine Data
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
Glucagon in humans is synthesized on chromosome 2 by α cells in the islets. A preprohormone is converted to a prohormone called glycentin, which is localized to the peripheral area of the secretory granules whereas glucagon is in the core of the granules. In several animal species, glucagon is synthesized in the GI tract.
Regulation of Gastrointestinal Neuropeptide Gene Expression and Processing
Published in Edwin E. Daniel, Neuropeptide Function in the Gastrointestinal Tract, 2019
The full-length translated VIP-PHI/PHM preprohormone is 170 amino acid residues long in man98,99 and probably also in rat,100 with the main difference being the encoding of PHM1—27 and PHI1—27 in man and rat, respectively, differing at 4 amino acid positions (see Figure 3).2 The preprohormone contains a possible N-glycosylation site,87,120 located at amino acid residues 68 to 70.98 The signal peptide is assigned to the amino acids 1 through 21 and is followed by an amino-terminal peptide of 58 amino acids (residues 22 to 79). This amino-terminal peptide is followed by a single basic Arg residue on the N-terminal side of PHM/PHI-27 and the presumptive amide donor Gly and the double base Lys-Arg (residue [109—110]) C-terminally. This processing site is followed by a 12-amino-acid-residue spacer peptide and the VIP sequence, surrounded N-terminally by the double bases Lys-Arg, contrary to only Arg in front of PHI/PHM-27, and C-terminally (similar to PHI/PHM-27) by Gly–Lys–Arg. The latter processing site is followed by a 15-amino-acid-residue flanking peptide C-terminally.
Developing mass spectrometry for the quantitative analysis of neuropeptides
Published in Expert Review of Proteomics, 2021
Christopher S. Sauer, Ashley Phetsanthad, Olga L. Riusech, Lingjun Li
This complexity inherent to all neuropeptidomic studies is exacerbated by the difficulties in determining possible neuropeptide sequences. Neuropeptides are produced by the select processing of precursor proteins (i.e. preprohormone) encoded within the genome [19]. These preprohormones contain a signaling sequence and the remaining prohormone. After cleavage of the signaling sequence, the prohormone is selectively and specifically cleaved by endopeptidases, such as various prohormone convertases, to produce several peptide sequences from a single precursor protein [20]. The peptides are then processed further and post-translationally modified to produce the bioactive neuropeptides [20]. The intricate pathways from genome to active neuropeptide, splice variants, and diversity of post-translational modifications lead to many possible peptide forms that are difficult to predict from genomics or even transcriptomics alone. This is compounded by the fact that many model organisms do not have a fully sequenced genome to use as a reliable starting point for predicting a full neuropeptide database, making neuropeptide studies even more challenging.