Everything about Peptide Hormone totally explained
Peptide hormones are a class of
peptides that are secreted into the blood stream and have
endocrine functions in living animals.
Like other
proteins, peptide
hormones are synthesized from
amino acids according to an
mRNA template, which is itself synthesized from a
DNA template inside the
cell's
nucleus. Peptide hormone precursors (pre-prohormones) are then processed in several stages, typically in the
endoplasmic reticulum, including removal of the
N-terminal signal sequence and sometimes
glycosylation, resulting in
prohormones. The prohormones are then packaged into membrane-bound secretory vesicles, which can be secreted from the cell by
exocytosis in response to specific stimuli.
These prohormones often contain superfluous amino acid residues that were needed to direct folding of the hormone molecule into its active configuration but have no function once the hormone folds. Specific
endopeptidases in the cell cleave the prohormone just before it's released into the
blood stream, generating the mature hormone form of the molecule. Mature peptide hormones then diffuse through the blood to all of the cells of the body, where they interact with specific
receptors on the surface of their target cells. Some peptide/
protein hormones (
angiotensin II,
basic fibroblast growth factor-2,
parathyroid hormone-related protein) also interact with
intracellular receptors located in the
cytoplasm or
nucleus by an
intracrine mechanism.
Notable peptide hormones
Several important peptide hormones are secreted from the pituitary gland. The
anterior pituitary secretes
luteinizing hormone and
follicle-stimulating hormone, which act on the
gonads,
prolactin, which acts on the
mammary gland,
adrenocorticotrophic hormone (ACTH), which acts on the
adrenal cortex to regulate the secretion of
glucocorticoids, and
growth hormone, which acts on
bone,
muscle, and the
liver. The
posterior pituitary gland secretes
antidiuretic hormone, also called vasopressin, and
oxytocin. Peptide hormones are produced by many different organs and tissues, however, including the
heart (
atrial-natriuretic peptide (ANP) or atrial natriuretic factor (ANF)) and
pancreas (
insulin and
somatostatin), the gastrointestinal tract (
cholecystokinin,
gastrin), and
adipose tissue stores (
leptin).
Some
neurotransmitters are secreted and released in a similar fashion to peptide hormones, and some '
neuropeptides' may be used as neurotransmitters in the
nervous system in addition to acting as hormones when released into the blood. When a peptide hormone binds to receptors on the surface of the cell, a
second messenger appears in the
cytoplasm, which triggers intracellular responses.
Further Information
Get more info on 'Peptide Hormone'.
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