octapeptide

オクタペプチド

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/08/01 13:49:30」(JST)

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"Peptides" redirects here. For the journal, see Peptides (journal).

A tetrapeptide (example Val-Gly-Ser-Ala) with
green marked amino end (L-Valine) and

blue marked carboxyl end (L-Alanine).

Peptides (from Gr.: πεπτός, peptós "digested"; derived from πέσσειν, péssein "to digest") are biologically occurring short chains of amino acid monomers linked by peptide (amide) bonds.

The covalent chemical bonds are formed when the carboxyl group of one amino acid reacts with the amine group of another. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a single peptide bond, followed by tripeptides, tetrapeptides, etc. A polypeptide is a long, continuous, and unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological oligomers and polymers, alongside nucleic acids, oligosaccharides and polysaccharides, etc.

Peptides are distinguished from proteins on the basis of size, and as an arbitrary benchmark can be understood to contain approximately 50 or fewer amino acids. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, or to another protein or other macromolecule (DNA, RNA, etc.), or to complex macromolecular assemblies. Finally, while aspects of the lab techniques applied to peptides versus polypeptides and proteins differ (e.g., the specifics of electrophoresis, chromatography, etc.), the size boundaries that distinguish peptides from polypeptides and proteins are not absolute: long peptides such as amyloid beta have been referred to as proteins, and smaller proteins like insulin have been considered peptides.

Amino acids that have been incorporated into peptides are termed "residues" due to the release of either a hydrogen ion from the amine end or a hydroxyl ion from the carboxyl end, or both, as a water molecule is released during formation of each amide bond. All peptides except cyclic peptides have an N-terminal and C-terminal residue at the end of the peptide (as shown for the tetrapeptide in the image).

Peptide classes

Peptides are divided into several classes, depending on how they are produced:

Milk peptides 

Two naturally occurring milk peptides are formed from the milk protein casein when digestive enzymes break this down; they can also arise from the proteinases formed by lactobacilli during the fermentation of milk.

Ribosomal peptides 

Ribosomal peptides are synthesized by translation of mRNA. They are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules. Some organisms produce peptides as antibiotics, such as microcins. Since they are translated, the amino acid residues involved are restricted to those utilized by the ribosome.

However, these peptides frequently have posttranslational modifications... such as phosphorylation, hydroxylation, sulfonation, palmitoylation, glycosylation and disulfide formation. In general, they are linear, although lariat structures have been observed. More exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids in platypus venom.

Nonribosomal peptides 

Nonribosomal peptides are assembled by enzymes that are specific to each peptide, rather than by the ribosome. The most common non-ribosomal peptide is glutathione, which is a component of the antioxidant defenses of most aerobic organisms. Other nonribosomal peptides are most common in unicellular organisms, plants, and fungi and are synthesized by modular enzyme complexes called nonribosomal peptide synthetases.

These complexes are often laid out in a similar fashion, and they can contain many different modules to perform a diverse set of chemical manipulations on the developing product. These peptides are often cyclic and can have highly complex cyclic structures, although linear nonribosomal peptides are also common. Since the system is closely related to the machinery for building fatty acids and polyketides, hybrid compounds are often found. The presence of oxazoles or thiazoles often indicates that the compound was synthesized in this fashion.

Peptones

See also Tryptone

Peptones are derived from animal milk or meat digested by proteolysis. In addition to containing small peptides, the resulting spray-dried material includes fats, metals, salts, vitamins and many other biological compounds. Peptones are used in nutrient media for growing bacteria and fungi.

Peptide fragments 

Peptide fragments refer to fragments of proteins that are used to identify or quantify the source protein. Often these are the products of enzymatic degradation performed in the laboratory on a controlled sample, but can also be forensic or paleontological samples that have been degraded by natural effects.

Peptide synthesis

Main article: Peptide synthesis

Solid-phase peptide synthesis on a rink amide resin using Fmoc-α-amine-protected amino acid

Peptides in molecular biology

Peptides received prominence in molecular biology for several reasons. The first is that peptides allow the creation of peptide antibodies in animals without the need of purifying the protein of interest. This involves synthesizing antigenic peptides of sections of the protein of interest. These will then be used to make antibodies in a rabbit or mouse against the protein.

Another reason is that peptides have become instrumental in mass spectrometry, allowing the identification of proteins of interest based on peptide masses and sequence.

Peptides have recently been used in the study of protein structure and function. For example, synthetic peptides can be used as probes to see where protein-peptide interactions occur- see the page on Protein tags.

Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases. For example, one of the most promising application is through peptides that target LHRH. These particular peptides act as an agonist, meaning that they bind to a cell in a way that regulates LHRH receptors. The process of inhibiting the cell receptors suggests that peptides could be beneficial in treating prostate cancer. However, additional investigations and experiments are required before the cancer-fighting attributes, exhibited by peptides, can be considered definitive.

Well-known peptide families

The peptide families in this section are ribosomal peptides, usually with hormonal activity. All of these peptides are synthesized by cells as longer "propeptides" or "proproteins" and truncated prior to exiting the cell. They are released into the bloodstream where they perform their signaling functions.

Tachykinin peptides

Main article: Tachykinin peptides

• Substance P
• Kassinin
• Neurokinin A
• Eledoisin
• Neurokinin B

Vasoactive intestinal peptides

Main article: Secretin family

• VIP (Vasoactive Intestinal Peptide; PHM27)
• PACAP Pituitary Adenylate Cyclase Activating Peptide
• Peptide PHI 27 (Peptide Histidine Isoleucine 27)
• GHRH 1-24 (Growth Hormone Releasing Hormone 1-24)
• Glucagon
• Secretin

Pancreatic polypeptide-related peptides

• NPY (NeuroPeptide Y)
• PYY (Peptide YY)
• APP (Avian Pancreatic Polypeptide)
• PPY Pancreatic PolYpeptide

Opioid peptides

Main article: Opioid peptide

• Proopiomelanocortin (POMC) peptides
• Enkephalin pentapeptides
• Prodynorphin peptides

Calcitonin peptides

• Calcitonin
• Amylin
• AGG01

Other peptides

• B-type Natriuretic Peptide (BNP) - produced in myocardium & useful in medical diagnosis
• Lactotripeptides - Lactotripeptides might reduce blood pressure, although the evidence is mixed.

Notes on terminology

Length:

• A polypeptide is a single linear chain of many amino acids, held together by amide bonds.
• A protein is one or more polypeptide (more than about 50 amino acids long).
• An oligopeptide consists of only a few amino acids (between two and twenty).

A tripeptide (example Val-Gly-Ala) with
green marked amino end (L-Valine) and

blue marked carboxyl end (L-Alanine)

Number of amino acids:

• A monopeptide has one amino acid.
• A dipeptide has two amino acids.
• A tripeptide has three amino acids.
• A tetrapeptide has four amino acids.
• A pentapeptide has five amino acids.
• A hexapeptide has six amino acids.
• A heptapeptide has seven amino acids.
• An octapeptide has eight amino acids (e.g., angiotensin II).
• A nonapeptide has nine amino acids (e.g., oxytocin).
• A decapeptide has ten amino acids (e.g., gonadotropin-releasing hormone & angiotensin I).
• An undecapeptide (or monodecapeptide) has eleven amino acids, a dodecapeptide (or didecapeptide) has twelve amino acids, a tridecapeptide has thirteen amino acids, and so forth.
• An icosapeptide has twenty amino acids, a tricontapeptide has thirty amino acids, a tetracontapeptide has forty amino acids, and so forth.

See also: IUPAC numerical multiplier

Function:

• A neuropeptide is a peptide that is active in association with neural tissue.
• A lipopeptide is a peptide that has a lipid connected to it, and pepducins are lipopeptides that interact with GPCRs.
• A peptide hormone is a peptide that acts as a hormone.
• A proteose is a mixture of peptides produced by the hydrolysis of proteins. The term is somewhat archaic.

Doping in sports

The term peptide has been used to mean secretagogue peptides and peptide hormones in sports doping matters: secretagogue peptides are classified as Schedule 2 (S2) prohibited substances on the World Anti-Doping Agency (WADA) Prohibited List, and are therefore prohibited for use by professional athletes both in and out of competition. Such secretagogue peptides have been on the WADA prohibited substances list since at least 2008. The Australian Crime Commission cited the alleged misuse of secretagogue peptides in Australian sport including growth hormone releasing peptides CJC-1295, GHRP-6, and GHSR (gene) hexarelin. There is ongoing controversy on the legality of using secretagogue peptides in sports.

See also

• Argireline
• Beefy meaty peptide
• Bis-peptide
• Epidermal Growth Factor
• Journal of Peptide Science
• Lactotripeptides
• Multifunctional peptides
• Neuropeptides
• Palmitoyl pentapeptide-4
• Pancreatic hormone
• Peptide Spectral Library
• Peptide synthesis
• Peptidomimetics (such as peptoids and β-peptides) to peptides, but with different properties.
• Protein tag, describing addition of peptide sequences to enable protein isolation or detection
• Ribosome
• Translation

References

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

• 1. アカラシアの病態生理および病因 pathophysiology and etiology of achalasia
• 2. 心臓におけるアンギオテンシンⅡの作用 actions of angiotensin ii on the heart
• 3. プリオンによる中枢神経系疾患 diseases of the central nervous system caused by prions
• 4. プリオンの生物学および遺伝学 biology and genetics of prions
• 5. アミロイド疾患の遺伝的要因 genetic factors in the amyloid diseases

English Journal

• Cholecystokinin-8 induces brain-derived neurotrophic factor expression in noradrenergic neuronal cells.

• Hwang CK, Kim do K, Chun HS.SourceDepartment of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
• Neuropeptides.Neuropeptides.2013 Aug;47(4):245-50. doi: 10.1016/j.npep.2013.04.002. Epub 2013 May 20.
• The sulfated cholecystokinin octapeptide (CCK-8S) is one of the most abundant CCK fragment in the brain, but the effects of CCK-8S on locus coeruleus (LC) noradrenergic (NA) neuronal cells activity have not been studied. In this study, we investigated the effects of CCK-8S on the expression of brain
• PMID 23702255

• Neurotensin and cholecystokinin contract gallbladder circular muscle in chickens.

• Degolier TF, Brown DR, Duke GE, Palmer MM, Swenson JR, Carraway RE.SourceDepartment of Biological Sciences, Bethel University, 3900 Bethel Drive, St. Paul, MN 55112;
• Poultry science.Poult Sci.2013 Aug;92(8):2156-62. doi: 10.3382/ps.2013-03079.
• The contractile effects of neurotensin (NT) and cholecystokinin octapeptide (CCK-8) on isolated circular smooth muscle strips of chicken gallbladder were investigated. The NT (0.25-300 nM) produced concentration-dependent contractions on smooth muscle with an EC50 of 8.5 nM (95% confidence limits =
• PMID 23873564

• Synthesis and antifungal activities of cyclic octa-lipopeptide burkholdine analogues.

• Konno H, Otsuki Y, Matsuzaki K, Nosaka K.SourceDepartment of Biological Engineering, Graduate School of Science and Technology, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan. Electronic address: konno@yz.yamagata-u.ac.jp.
• Bioorganic & medicinal chemistry letters.Bioorg Med Chem Lett.2013 Jul 15;23(14):4244-7. doi: 10.1016/j.bmcl.2013.04.091. Epub 2013 May 14.
• Synthesis and antifungal activity of cyclic octapeptide derivatives of burkholdines are described. To construct cyclic octapeptides, the combination of Fmoc-SPPS and cyclization with DIC/HOBt in the solution phase was employed. Synthesized peptides were evaluated for antifungal activity with MIC val
• PMID 23769641

Japanese Journal

• Genetic Diversity in the Prion Protein Gene (<i>PRNP</i>) of Domestic Cattle and Water Buffaloes in Vietnam, Indonesia and Thailand

• Journal of Veterinary Medical Science 76(7), 1001-1008, 2014
• NAID 130003391317

• Biological and Biochemical Characterization of Mice Expressing Prion Protein Devoid of the Octapeptide Repeat Region after Infection with Prions

• PLoS ONE 7(8), e43540, 2012-08-21
• NAID 120005121768

• Biological and Biochemical Characterization of Mice Expressing Prion Protein Devoid of the Octapeptide Repeat Region after Infection with Prions

• PLOS ONE 7(8), 2012
• NAID 120005597759

Related Links

• Octapeptide | Definition of Octapeptide by Merriam-Webster

:a protein fragment or molecule (as oxytocin or vasopressin) that consists of eight amino acids linked in a polypeptide chain ... Seen and Heard What made you want to look up octapeptide? Please tell us where you read or heard it ...

• Octapeptide - definition of octapeptide by The Free Dictionary

oc·ta·pep·tide (ŏk′tə-pĕp′tīd) n. A polypeptide, such as angiotensin, that is composed of eight amino acids. octapeptide (ˌɒktəˈpɛptaɪd) ... Octreotide, an octapeptide that mimics natural somatostatin, has been widely used in the ...

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拡張検索	「cholecystokinin octapeptide」

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コレシストキニンオクタペプチド、コレシストキニン-8

関

CCK-8、cholecystokinin 8、sincalide