A number of polypeptidic hormones, mainly expressed in the intestine or the
pancreas, belong to a group of structurally related peptides [1,2]. Members of
this family are:
Glucagon, which promotes hydrolysis of glycogen and lipids, and raises the
blood sugar level.
Glucagon-like peptide 1 (GLP-1), a peptide of unknown function processed
from the same precursor protein as that of glucagon.
Glucagon-like peptide 2 (GLP-2), a peptide of unknown function also
processed from the glucagon precursor protein but which, in contrast to
GLP-1, is only found in mammals.
Gastric inhibitory polypeptide (GIP), which is a potent stimulator of
insulin secretion and a relatively poor inhibitor of gastric acid
secretion.
Secretin, which stimulates formation of NaHCO(3)-rich pancreatic juice and
secretion of NaHCO(3)-rich bile as well as inhibiting HCl production by the
stomach.
Vasoactive intestinal peptide (VIP), which causes vasodilatation, lowers
arterial blood pressure, stimulates myocardial contractility, increases
glycogenolysis and relaxes some smooth muscles.
Peptide PHI-27, a vasodilator peptide which is coded by the same precursor
protein as that of VIP.
Growth hormone-releasing factor (GRF) (also known as somatoliberin), which
is released by the hypothalamus and acts on the adenohypophyse to stimulate
the secretion of growth hormone.
Helospectin (exendin-1), helodermin (exendin-2), exendin-3, and exendin-4
from the venom of gila monsters. The exendins are peptides with a VIP/
secretin biological activity [4].
A peptide produced by the X-cells of the islets of ratfish pancreas [5].
As a pattern for this family of peptides (which are from 30 to 45 amino acid
residues long), we used the more or less conserved first ten positions of the
N-terminal as well as a conserved hydrophobic residue in position 23.
Eng J. Kleinman W.A. Singh L. Singh G. Raufman J.-P.
Title
Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom. Further evidence for an exendin receptor on dispersed acini from guinea pig pancreas.
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