This MedLibrary.org supplementary page on Protein hormone is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
Peptide hormones are a class of peptides that are secreted into the blood stream and have endocrine functions in living animals.[1]
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.[2]
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 is 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.[3]
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).[4][5]
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.[6]
References
- ^ Peptide Hormone Secretion/Peptide Hormone Action: A Practical Approach, K. Siddle, J. C. Hutton, Oxford University Press, 1991, ISBN:0199630739.
- ^ Peptide Hormone Secretion: A Practical Approach, J. C. Hutton, Oxford University Press, 1991, ISBN:0199630682.
- ^ The Endocrine System in Sports and Exercise, William J. Kraemer, Alan D. Rogol, Blackwell Publishing, 2005, ISBN:1405130172.
- ^ Dictionary of Biological Psychology, Philip Winn, Taylor and Francis, 2001, ISBN:0415136067.
- ^ McGraw-Hill Encyclopedia of Science & Technology, Sybil P. Parker, McGraw-Hill, 1997, ISBN:0079115047.
- ^ The Practice of Medicinal Chemistry, C. G. Wermuth, Academic Press, 2003, ISBN:0127444815.
|
|||||||||||||||||||||||
Wikipedia content modification information:
- This page was last modified on 17 September 2008, at 04:11.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Protein hormone".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.