8 Peptide Hormones
8.1
8.2
8.2.1
8.2.2
8.2.3
8.3
8.3.1
8.3.2
8.3.3
8.3.4
8.4
8.4.1
8.4.2
Hormones of the Neurohypophysis
Hormones of the Hypothalamus and Urophysis
Release and Release-Inhibiting Factors
Peptides from the Hypothalamus, Gut
and Frog Skin
Hormones of the Urophysis
Hormones of the Adenohypophysis
Glycoproteins of the Adenohypophysis
Pro-Opiomelanocortins
Opioids
Growth Hormone, Prolactin and Lactogen
Hormones of the Stomach, Intestine and Pancreas
The Gastrin-Cholecystokinin Family
The Insulin Family
Next to the steroids, the most important signalling molecules in animals are peptides. Their high
information content and unambiguous genetic
coding make them particularly suitable for signal
transmission in the body. In addition to their classical endocrine functions, peptides also play a
role as neurotransmitters, neuromodulators and
growth substances. This variety of functions is
reflected in the term "regulatory peptides". In
the vertebrates, we now know more about regulatory peptides than all other types of signalling
molecule put together (steroids, amines and
amino acids), and they continue to be discovered.
The concentrations of regulatory peptides, even
in organs of synthesis or storage, are mostly of the
order of nanograms per tissue; consequently,
their isolation often requires extraction from
thousands of individuals, especially when dealing
with small invertebrates. The paucity of material
available hinders direct sequencing; this is made
still more problematic by the blocked N- and Cterminals of many peptide hormones. As a result,
the investigation of regulatory peptides relies
more and more upon the determination of cDNA
and gene sequences. The ever-increasing sophistication of analytical methods has led to a drastic
increase in the number of known peptides in the
last two decades, but in many cases neither the
action spectrum nor biological role has yet been
8.4.3
8.4.4
8.S
8.6
8.7
8.8
8.8.1
8.8.2
8.9
8.9.1
8.9.2
8.9.3
The Glucagon-Secretin Family
The Family of Pancreas Polypeptides
Peptides Regulating Blood Pressure
Calcitonins and Parathormone
Growth Factors
Peptide Hormones of Invertebrates
Peptide Hormones of Molluscs
Peptide Hormones of Arthropods
Hormone Receptors
G-Protein-Linked Receptors
Nicotinic Acetylcholine Receptors
Insulin Receptors
References
defined. The following sections deal only with
those peptides for which some comparative biochemical data are available [73, 81].
The sizes of the regulatory peptides range from
tripeptides to polypeptides of over 100 amino
acids, which as a rule also bear carbohydrate
chains. The peptides usually arise from significantly larger precursors (prepro-hormones). The
primary translation products begin, as in the
majority of secreted proteins, with a pre- or signalling sequence which is removed by a signal
protease during translation. The peptide precursor is modified in the endoplasmic reticulum and
Golgi apparatus by N- and O-glycosylation, by
the phosphorylation of certain serines or threonines, and by the sulphation of certain tyrosine residues. The precursor is endoproteolytically
cleaved in the secretory granules, or sometimes
this has already occurred in the Golgi apparatus.
The responsible proteases are highly specific, the
cleavage sites in the precursor sequence being
marked by pairs of basic amino acids (arginine,
lysine) or by single arginine residues. In some
cases, a whole series of peptides of varying
length, but with the same active sequence, is produced by irregular cleavage of the pro-protein.
One of the proteases involved in this process is
carboxypeptidase E, which belongs to the same
family as the carboxypeptidases A and B,
8.1
8.2
8.2.1
8.2.2
8.2.3
8.3
8.3.1
8.3.2
8.3.3
8.3.4
8.4
8.4.1
8.4.2
Hormones of the Neurohypophysis
Hormones of the Hypothalamus and Urophysis
Release and Release-Inhibiting Factors
Peptides from the Hypothalamus, Gut
and Frog Skin
Hormones of the Urophysis
Hormones of the Adenohypophysis
Glycoproteins of the Adenohypophysis
Pro-Opiomelanocortins
Opioids
Growth Hormone, Prolactin and Lactogen
Hormones of the Stomach, Intestine and Pancreas
The Gastrin-Cholecystokinin Family
The Insulin Family
Next to the steroids, the most important signalling molecules in animals are peptides. Their high
information content and unambiguous genetic
coding make them particularly suitable for signal
transmission in the body. In addition to their classical endocrine functions, peptides also play a
role as neurotransmitters, neuromodulators and
growth substances. This variety of functions is
reflected in the term "regulatory peptides". In
the vertebrates, we now know more about regulatory peptides than all other types of signalling
molecule put together (steroids, amines and
amino acids), and they continue to be discovered.
The concentrations of regulatory peptides, even
in organs of synthesis or storage, are mostly of the
order of nanograms per tissue; consequently,
their isolation often requires extraction from
thousands of individuals, especially when dealing
with small invertebrates. The paucity of material
available hinders direct sequencing; this is made
still more problematic by the blocked N- and Cterminals of many peptide hormones. As a result,
the investigation of regulatory peptides relies
more and more upon the determination of cDNA
and gene sequences. The ever-increasing sophistication of analytical methods has led to a drastic
increase in the number of known peptides in the
last two decades, but in many cases neither the
action spectrum nor biological role has yet been
8.4.3
8.4.4
8.S
8.6
8.7
8.8
8.8.1
8.8.2
8.9
8.9.1
8.9.2
8.9.3
The Glucagon-Secretin Family
The Family of Pancreas Polypeptides
Peptides Regulating Blood Pressure
Calcitonins and Parathormone
Growth Factors
Peptide Hormones of Invertebrates
Peptide Hormones of Molluscs
Peptide Hormones of Arthropods
Hormone Receptors
G-Protein-Linked Receptors
Nicotinic Acetylcholine Receptors
Insulin Receptors
References
defined. The following sections deal only with
those peptides for which some comparative biochemical data are available [73, 81].
The sizes of the regulatory peptides range from
tripeptides to polypeptides of over 100 amino
acids, which as a rule also bear carbohydrate
chains. The peptides usually arise from significantly larger precursors (prepro-hormones). The
primary translation products begin, as in the
majority of secreted proteins, with a pre- or signalling sequence which is removed by a signal
protease during translation. The peptide precursor is modified in the endoplasmic reticulum and
Golgi apparatus by N- and O-glycosylation, by
the phosphorylation of certain serines or threonines, and by the sulphation of certain tyrosine residues. The precursor is endoproteolytically
cleaved in the secretory granules, or sometimes
this has already occurred in the Golgi apparatus.
The responsible proteases are highly specific, the
cleavage sites in the precursor sequence being
marked by pairs of basic amino acids (arginine,
lysine) or by single arginine residues. In some
cases, a whole series of peptides of varying
length, but with the same active sequence, is produced by irregular cleavage of the pro-protein.
One of the proteases involved in this process is
carboxypeptidase E, which belongs to the same
family as the carboxypeptidases A and B,