BIOC 462B: Dr' Tischler

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BIOC 462B Dr. Tischler
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PEPTIDE-AMINE HORMONE BIOSYNTHESIS
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• Objectives
•  
• Describe the acute and chronic regulation of
  epinephrine synthesis in the chromaffin cells of
  the adrenal medulla.
• Discuss the roles of Na-I symport, peroxidase and
  thyroglobulin in the formation of thyroid
  hormones and how this process is regulated by
  thyroid stimulating hormone in the thyroid
  follicular cell.
• Outline the steps in the biosynthesis and release
  of insulin by the pancreatic beta-cell including
  the intracellular location of each step.
• Discuss how signaling via cyclic AMP controls the
  synthesis and release of growth hormone by
  somatotropic cells of the anterior pituitary in
  the brain.

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Figure 1. Biosynthesis of epinephrine.
Abbreviations BH2, dihydrobiopterin BH4,
tetrahydrobiopterin PNMT, phenylethanolamine
N-methyl transferase SAH, S-adenosylhomocysteine
SAM, S-adenosylmethionine.
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Figure 2. Regulation of the release of
catecholamines and synthesis of epinephrine in
the adrenal medulla chromaffin cell.
Tyrosine
TH
L-Dopa
DPN
DD
induction
DPN ?DH NE
Neuron
granule
PNMT
Epinephrine
NE
E E E NE E E
promotes exocytosis
neuro- secretory granules
Adrenal Medulla Chromaffin Cell
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Figure 3. Iodine metabolism in the thyroid
follicle and its stimulation by TSH
Extracellular Space (COLLOID)
I
Iodination
I-
Peroxidase
Peroxidase
Peroxidase
Secreted to Colloid
THYROID FOLLICULAR CELL
H2O2
Lysosomes
Secondary Lysosomes
Mitochondrion
Symport
Concentration
Extracellular Space (BLOOD SIDE)
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Figure 4. Insulin and its precursor forms
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Figure 5. Structural components (italicized) of
the pancreatic ?-cell involved in glucose-induced
biosynthesis and release of insulin.
Biological structures
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GHRH
SOMATOTROPE
Figure 6. Model for the effects of growth
hormone releasing hormone (GHRH) on the adenylyl
cyclase-cyclic AMP pathway in the somatotrope
cell in the control of growth hormone (GH)
synthesis and secretion.
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CREB Cyclic AMP Responsive
Element Binding protein
ACTIVE adenylyl cyclase
NUCLEUS
Enhanced transcription of GH gene
Figure 6. Controlling the synthesis and secretion
of growth hormone (GH)
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POMC
?
products from corticotroph controlled by CRH
Signal peptide
select neurons process POMC differently secrete
?-endorphin or ?MSH into CNS
CLIP corticotropin-like intermediary peptide
Figure 7. Proopiomelanocortin (POMC) is a
polypeptide product encoded by a single gene.
The dark vertical bars represent proteolytic
cleavage sites for specific enzymes. These sites
consist of pairs of basic amino acids (Arg, Lys)
just as occurs in the processing of glucagon and
vasopressin.