Difference between revisions of "Peptide" - New World Encyclopedia

Latest revision as of 20:16, 14 April 2015

Peptides are short chains of amino acids linked together via peptide bonds and having a defined sequence. Peptides function primarily as signaling molecules in animals or as antibiotics in some lower organisms.

The number of amino acid molecules present in a peptide is indicated by a prefix. For example, a dipeptide has two amino acids; a tripeptide has three. An oligopeptide contains a few molecules; a polypeptide contains many. Peptides generally contain fewer than 30 amino acid residues, while polypeptides contain as many as 4000. The distinction between polypeptides and proteins is largely academic and imprecise, and the two terms are sometimes used interchangeably. However, there is a movement within the scientific community to define proteins as polypeptides (or complexes of polypeptides) with three-dimensional structure.

In animals, peptides are involved in the complex coordination of the body, with three major classes of peptides involved in signaling:

Peptide hormones, which function as chemical messengers between cells. Growth hormone, for example, is involved in the general stimulation of growth, and insulin and glucagon are well known peptide hormones.
Neuropeptides, which are peptides found in neural tissue. Endorphins and enkephalins are neuropeptides that mimic the effects of morphine, inhibiting the transmission of pain signals. The peptides vasopressin and oxytoxin have been linked to social behaviors such as pair-bonding.
Growth factors, which play a role in regulating animal cell growth and differentiation.

Human creativity has led to peptides being important tools for understanding protein structure and function. Peptide fragments are components of proteins that researchers use to identify or quantify the source protein. Often these fragments are the products of enzymatic degradation performed in the laboratory on a controlled sample, but they can also be forensic or paleontological samples that have been degraded by natural effects. Peptides also allow antibodies to be generated without the need to purify the protein of interest, by making antigenic peptides of sections of the protein.

The components of peptides

Summary of the formation of a peptide bond. Click on image to see the reaction.

Like proteins, peptides are built from combinations of 20 different amino acids, which are organic molecules composed of an amino group (-NH2), a carboxylic acid group (-COOH), and a unique R group, or side chain. Two amino acids (specifically, alpha-amino acids) are linked together by a peptide bond. A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one amino acid reacts with the amino group of the other amino acid; the resulting CO-NH bond is called a peptide bond. An amino acid residue is what is left of an amino acid once it has coupled with another amino acid to form a peptide bond.

Peptides are then created by the polymerization of amino acids, a process in which amino acids are joined together in chains. Shorter strings of amino acids may be referred to as peptides, or, less commonly, oligopeptides.

Peptide synthesis

Peptides are synthesized from amino acids according to an mRNA template, which is itself synthesized from a DNA template inside the cell's nucleus. The precursors of ribosomal peptides are processed in several stages in the endoplasmic reticulum, resulting in "propeptides." These propeptides are then packaged into membrane-bound secretory vesicles, which can be released into the bloodstream in response to specific stimuli.

Nonribosomal peptides, found primarily in fungi, plants, and, unicellular organisms are synthesized using a modular enzyme complex (which functions much like a conveyor belt in a factory). All of these complexes are laid out in a similar fashion, and they may contain many different modules to perform a diverse set of chemical manipulations on the developing peptide. Nonribosomal peptides often have highly complex cyclic structures, although linear nonribosomal peptides are also common.

Some key peptide groups and their biological function

Peptides comprise the widest variety of signaling molecules in animals. The three major classes of peptides are peptide hormones, neuropeptides, and polypeptide growth factors. Many peptides are found in both the brain and non neural tissues. The blood-brain barrier prevents peptide hormones traveling in the blood from entering the brain, so that they do not interfere with the functioning of the central nervous system.

Peptide hormones

Peptide hormones are a class of peptides that function in living animals as chemical messengers from one cell (or group of cells) to another. Well-known peptide hormones include insulin, glucagon, and the hormones secreted from the pituitary gland, an endocrine gland about the size of a pea that sits in a small, bony cavity at the base of the brain. The latter include follicle stimulating hormone (FSH), growth hormone, and vasopressin. However, peptide hormones are produced by many different organs and tissues, including the heart, pancreas, and gastrointestinal tract.

Neuropeptides

A neuropeptide is any of the variety of peptides found in neural tissue. Approximately 100 different peptides are currently known to be released by different populations of neurons in the mammalian brain. Some neuropeptides act both as neurotransmitters in the nervous system and as neurohormones that act on distant cells.

Neurons use many different chemical signals to communicate information, including neurotransmitters, peptides, cannabinoids, and even some gases, like nitric oxide. Peptide signals play a role in information processing distinct from that of conventional neurotransmitters. While neurotransmitters generally affect the excitability of other neurons by depolarizing them or hyperpolarizing them, peptides have much more diverse effects; among other things, they can affect gene expression, local blood flow, and the formation of synapses.

Neurons very often produce both a conventional neurotransmitter (such as glutamate, GABA or dopamine) and one or more neuropeptides. Peptides are generally packaged in large dense-core vesicles, while the co-existing neurotransmitters are contained in small synaptic vesicles.

Vasopressin and oxytoxin

The neuropeptide Arginine vasopressin (AVP), also known as argipressin or antidiuretic hormone (ADH), is a hormone found in humans. It is mainly released when the body is low on water; it stimulates water reabsorption in the kidneys. It performs diverse actions when released in the brain, and has been implicated in memory formation, aggression, blood pressure regulation, and temperature regulation. Similar vassopressins are found in other mammalian species.

In recent years, there has been particular interest in the role of vasopressin in social behavior. It is thought that vasopressin, released into the brain during sexual activity, initiates and sustains patterns of activity that support the pair-bond between the sexual partners; in particular, vasopressin seems to induce the male to become aggressive towards other males. Evidence for this connection comes from experimental studies on several species which indicate that the precise distribution of vasopressin and vasopressin receptors in the brain is associated with species-typical patterns of social behavior. In particular, there are consistent differences between monogamous species and promiscuous species in the distribution of vasopressin receptors, and sometimes in the distribution of vasopressin-containing axons, even when closely-related species are compared. Moreover, studies involving either injecting vasopressin agonists into the brain or blocking the actions of vasopressin support the hypothesis that vasopressin is involved in aggression towards other males. There is also evidence that differences in the vasopressin receptor gene between individual members of a species might be predictive of differences in social behavior.

Oxytocin is a mammalian hormone involved in the stimulation of smooth muscle contraction that also acts as a neurotransmitter in the brain. In women, it is released mainly after distension of the cervix and vagina during labor, and after stimulation of the nipples, facilitating birth and breastfeeding, respectively.

Opioid peptides

Opioid peptides produced in the body include endorphins and enkephalins. Opioid peptides act as natural pain killers, or opiates, decreasing pain responses in the central nervous system.

Growth factors

Polypeptide growth factors control animal cell growth and differentiation. Nerve growth factor (or NGF) is involved in the development and survival of neurons, while platelet-derived growth factor (PDGF) participates in blood clotting at the site of a wound. PDGF stimulates the spread of fibroblasts in the vicinity of the clot, facilitating the regrowth of the damaged tissue.

Given the role of polypeptide growth factors in controlling cell proliferation, abnormalities in growth factor signaling are the basis for a variety of diseases, including many types of cancer.

Peptides are an important research tool

Peptides have received prominence in molecular biology in recent times for several reasons:

Peptides allow researchers to generate antibodies in animals without the need to purify the protein of interest. The researcher can simply make antigenic peptides of sections of the protein.
Peptides have become instrumental in mass spectrometry, allowing the identification of proteins of interest based on peptide masses and sequences.
Peptides have recently been used in the study of protein structure and function. For example, synthetic peptides can be used as probes to determine where protein-peptide interactions occur.
Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases.

Peptide families

Below is a more detailed list of the major families of ribosomal peptides:

Vasopressin and oxytocin
- Vasopressin
- Oxytocin

The Tachykinin peptides
- Substance P
- Kassinin
- Neurokinin A
- Eledoisin
- Neurokinin B

Vasoactive intestinal peptides
- VIP (Vasoactive intestinal peptide)
- PACAP (Pituitary adenylate cyclase activating peptide)
- PHI 27
- PHM 27
- GHRH 1-24 (Growth hormone releasing hormone 1-24)
- Glucagon
- Secretin

Pancreatic polypeptide-related peptides
- NPY
- PYY (Peptide YY)
- APP (Avian pancreatic polypeptide)
- HPP (Human pancreatic polypeptide)

Opioid peptides
- Proopiomelanocortin (POMC) Peptides
- The Enkephalin pentapeptides
- The Prodynorphin peptides

Calcitonin peptides
- Calcitonin
- Amylin
- AGG01

References
ISBN links support NWE through referral fees

Cooper, G. M., and R. E. Hausman. 2004. The Cell: A Molecular Approach, 3rd edition. Washington, DC: ASM Press & Sunderland, MA: Sinauer Associates. ISBN 0878932143
Lodish, H., D. Baltimore, A. Berk, S. L. Zipursky, P. Matsudaira, and J. Darnell. 1996. Molecular Cell Biology. Oxford: W H Freeman and Company. ISBN 0716727110
Stryer, L. 1995. Biochemistry, 4th edition. New York, NY: W.H. Freeman. ISBN 0716720094

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@@ Line 1: / Line 1: @@
-{{Claimed}}{{Contracted}}
+{{Paid}}{{Approved}}{{Images OK}}{{Submitted}}{{copyedited}}
-'''Peptides''' (from the Greek πεπτος, "digestible") are the family of short [[molecules]] formed from the linking, in a defined order, of various α-[[amino acid]]s. The link between one amino acid residue and the next is an [[amide]] [[chemical bond|bond]] and is sometimes referred to as a [[peptide bond]].
+'''Peptides''' are short chains of [[amino acid]]s linked together via [[#The components of peptides|peptide bond]]s and having a defined sequence. Peptides function primarily as '''[[signaling molecules]]''' in [[animal]]s or as [[antibiotic]]s in some lower [[organism]]s.
-[[Proteins]] are '''polypeptide''' molecules (or consist of multiple polypeptide subunits). The distinction is that peptides are short and proteins are long. There are several different conventions to determine these, all of which have flaws. In order for a polypeptide to be a protein, it has to have some sort of biological function in the body. {{fact}}
+The number of amino acid molecules present in a peptide is indicated by a prefix. For example, a ''dipeptide'' has two amino acids; a ''tripeptide'' has three. An ''oligopeptide'' contains a few molecules; a ''polypeptide'' contains many. Peptides generally contain fewer than 30 amino acid residues, while polypeptides contain as many as 4000. The distinction between polypeptides and [[protein]]s is largely academic and imprecise, and the two terms are sometimes used interchangeably. However, there is a movement within the scientific community to define proteins as polypeptides (or complexes of polypeptides) with three-dimensional structure.
-One convention is that those peptide chains that are short enough to be made synthetically from the constituent [[amino acid]]s are called peptides rather than proteins. However, with the advent of better synthetic techniques, peptides as long as hundreds of amino acids can be made, including full proteins like [[ubiquitin]]. [[Native chemical ligation]] has given access to even longer proteins, so this convention seems to be outdated.
+In animals, peptides are involved in the complex coordination of the body, with three major classes of peptides involved in signaling:
+*'''[[Peptide hormones]]''', which function as chemical messengers between [[cell (biology)|cells]]. [[Growth hormone]], for example, is involved in the general stimulation of growth, and [[insulin]] and [[glucagon]] are well known peptide hormones.
+*'''[[Neuropeptides]]''', which are peptides found in [[neural tissue]]. [[Endorphin]]s and [[enkephalin]]s are neuropeptides that mimic the effects of [[morphine]], inhibiting the transmission of [[pain]] signals. The peptides [[vasopressin]] and [[oxytoxin]] have been linked to social behaviors such as pair-bonding.
+*'''[[Growth factors]]''', which play a role in regulating animal cell growth and differentiation.
+{{toc}}
+Human creativity has led to peptides being important tools for understanding protein structure and function. '''Peptide fragments''' are components of proteins that researchers use to identify or quantify the [[source protein]]. Often these fragments are the products of enzymatic degradation performed in the laboratory on a controlled sample, but they can also be forensic or paleontological samples that have been degraded by natural effects. Peptides also allow [[antibody|antibodies]] to be generated without the need to purify the protein of interest, by making [[antigen|antigenic]] peptides of sections of the protein.
-Another convention places an informal dividing line at approximately 50 amino acids in length (some people claim shorter lengths). However, this definition is somewhat arbitrary — some peptides such as [[amyloid beta|alzheimer's beta peptide]] can be considered proteins and some proteins (such as [[insulin]]) are close to the upper limit for peptides. Because of the arbitrary nature of this definition, there is considerable movement within the scientific community to ascribe the more-specific definition that "a peptide is an amino acid molecule without secondary structure; on gaining defined structure, it is a protein." Thus the same molecule can be either a peptide or a protein depending on its environment, though there are peptides that cannot be proteins.
+== The components of peptides ==
+[[Image:Peptide_bonding.gif|thumb|Summary of the formation of a peptide bond. Click on image to see the reaction.]]
+Like [[protein]]s, peptides are built from combinations of 20 different amino acids, which are organic molecules composed of an amino group (-NH2), a [[carboxylic acid]] group (-COOH), and a unique R group, or side chain. Two [[amino acid]]s (specifically, alpha-amino acids) are linked together by a peptide bond. A [[peptide bond]] is a chemical bond formed between two [[molecule]]s when the carboxyl group of one amino acid reacts with the amino group of the other amino acid; the resulting CO-NH bond is called a peptide bond. An amino acid residue is what is left of an amino acid once it has coupled with another amino acid to form a peptide bond.
-==Peptide classes==
+Peptides are then created by the [[polymer]]ization of amino acids, a process in which amino acids are joined together in chains. Shorter strings of amino acids may be referred to as peptides, or, less commonly, oligopeptides.
-There are three large classes of peptides, according to how they are produced:
-; Ribosomal peptides : Are synthesized by [[Translation (genetics)|translation]] of [[mRNA]]. They are often subjected to [[proteolysis]] to generate the mature form. These function, typically in higher organisms, as [[hormone]]s and signaling molecules. Some lower organisms produce peptides as [[antibiotic]]s, such as [[microcin J25]]. Since they are translated, the [[amino acid residue]]s involved are restricted to the 20 amino acids (plus [[selenomethionine]] and [[pyrrolysine]]), and [[posttranslational modification]]s thereof, such as [[phosphorylation]], [[hydroxylation]], [[sulfonation]], [[disulfide bridge|disulfide]] formation, etc. In general, they are linear, although [[lariat]] structures are common.  More exotic manipulations do occur, however, such as racemization (as in [[platypus]] [[venom]]) or usage of nonribosmal peptide modules (see below) (as in [[bistratamide]] a).
+==Peptide synthesis==
+Peptides are synthesized from amino acids according to an [[mRNA]] template, which is itself synthesized from a [[DNA]] template inside the [[cell (biology)|cell]]'s nucleus. The precursors of '''ribosomal peptides''' are processed in several stages in the [[endoplasmic reticulum]], resulting in "propeptides." These propeptides are then packaged into membrane-bound secretory [[vesicle]]s, which can be released into the bloodstream in response to specific stimuli.
-; [[Nonribosomal peptide]]s : Are synthesized using a [[Modularity (biology)|modular]] enzyme complex (which functions much like a conveyor belt on a factory). Nonribosomal peptides and are confined primarily to [[unicellular organism]]s, [[plant]]s, and [[fungi]].  All of these complexes are laid out in a similar fashion, and they can contain many different modules to perform  a divdrse set of chemical manipulations on the developing product. In general, these peptides are [[Cyclic compound|cyclic]] (often with highly-complex cyclic structures), although linear nonribosomal peptides are common. Since the system is modular and closely related to the machinery for building [[fatty acid]]s and [[polyketide]]s, hybrid compounds are often found. [[Oxazoles]], [[thiazoles]], and their reduced counterparts often indicate that the compound was synthesized in this fashion.
+'''Nonribosomal peptides,''' found primarily in [[fungi]], [[plant]]s, and, unicellular organisms are synthesized using a modular enzyme complex (which functions much like a conveyor belt in a factory). All of these complexes are laid out in a similar fashion, and they may contain many different modules to perform a diverse set of chemical manipulations on the developing peptide. Nonribosomal peptides often have highly complex cyclic structures, although linear nonribosomal peptides are also common.
-; Digested peptides : Are the result of nonspecific proteolysis as part of the digestive cycle. It has also been documented that, when certain food proteins such as [[gluten]], [[casein]], [[egg (food)|egg]] protein, and [[spinach]] protein are broken down, [[opioid peptides]] are formed. These peptides mimic the effects of [[morphine]], and those individuals that are unable to break them down will experience mental illness. These peptides are quite short and are given names such as [[casomorphine]], [[gluten exorphine]], and [[dermorphine]]. Ultimately digested peptides are ribosomal peptides, although they aren't made on the ribosome of the organism that contains them.
+==Some key peptide groups and their biological function==
+Peptides comprise the widest variety of [[signaling molecules]] in animals. The three major classes of peptides are ''peptide hormones,'' ''neuropeptides,'' and ''polypeptide growth factors.'' Many peptides are found in both the brain and non neural tissues. The [[blood-brain barrier]] prevents peptide hormones traveling in the [[blood]] from entering the [[brain]], so that they do not interfere with the functioning of the [[central nervous system]].
-; Peptide Fragments : refer to fragments of proteins which 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 which have been degraded by natural effects.
+=== Peptide hormones ===
+'''Peptide hormones''' are a class of peptides that function in living [[animal]]s as chemical messengers from one cell (or group of cells) to another. Well-known peptide hormones include [[insulin]], [[glucagon]], and the hormones secreted from the [[pituitary gland]], an [[endocrine gland]] about the size of a pea that sits in a small, bony cavity at the base of the [[brain]]. The latter include [[follicle stimulating hormone]] (FSH), [[growth hormone]], and [[vasopressin]]. However, peptide hormones are produced by many different [[organ]]s and [[tissue]]s, including the [[heart]], [[pancreas]], and [[gastrointestinal tract]].
-== Peptides in Molecular Biology ==
+=== Neuropeptides ===
-Peptides have received prominence in molecular biology in recent times for several reasons. The first and most important is that peptides allow the creation of antibodies in animals without the need to purify the [[protein]] of interest. One can simply make antigenic peptides of sections of the protein of interest. These will suffice in making antibodies in a rabbit or mouse against the protein.
+A '''neuropeptide''' is any of the variety of peptides found in [[neural tissue]]. Approximately 100 different peptides are currently known to be released by different populations of neurons in the [[mammal]]ian brain. Some neuropeptides act both as [[neurotransmitter]]s in the [[nervous system]] and as neurohormones that act on distant cells.
-Another reason is that peptides have become instrumental in [[mass spectrometry]], allowing the identification of proteins of interest based on peptide masses and sequence.
+[[Neuron]]s use many different chemical signals to communicate information, including neurotransmitters, peptides, [[cannabinoids]], and even some gases, like [[nitric oxide]]. Peptide signals play a role in information processing distinct from that of conventional neurotransmitters. While neurotransmitters generally affect the excitability of other neurons by depolarizing them or hyperpolarizing them, peptides have much more diverse effects; among other things, they can affect gene expression, local blood flow, and the formation of [[synapse]]s.
-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.
+Neurons very often produce both a conventional neurotransmitter (such as [[glutamate]], [[GABA]] or [[dopamine]]) and one or more neuropeptides. Peptides are generally packaged in large dense-core vesicles, while the co-existing neurotransmitters are contained in small synaptic vesicles.
-Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases.
+====Vasopressin and oxytoxin====
+The neuropeptide '''Arginine vasopressin''' (AVP), also known as '''argipressin''' or '''antidiuretic hormone''' (ADH), is a [[hormone]] found in [[human]]s. It is mainly released when the body is low on [[water]]; it stimulates water reabsorption in the [[kidney]]s. It performs diverse actions when released in the brain, and has been implicated in [[memory]] formation, aggression, blood pressure regulation, and temperature regulation. Similar vassopressins are found in other mammalian species.
-==Peptide families==
+In recent years, there has been particular interest in the role of vasopressin in [[social behavior]]. It is thought that vasopressin, released into the brain during sexual activity, initiates and sustains patterns of activity that support the pair-bond between the sexual partners; in particular, vasopressin seems to induce the male to become aggressive towards other males. Evidence for this connection comes from experimental studies on several species which indicate that the precise distribution of vasopressin and vasopressin receptors in the brain is associated with species-typical patterns of social behavior. In particular, there are consistent differences between monogamous species and promiscuous species in the distribution of vasopressin receptors, and sometimes in the distribution of vasopressin-containing [[axons]], even when closely-related species are compared. Moreover, studies involving either injecting vasopressin agonists into the brain or blocking the actions of vasopressin support the hypothesis that vasopressin is involved in aggression towards other males. There is also evidence that differences in the vasopressin receptor gene between individual members of a species might be predictive of differences in social behavior.
-The peptide families in this section are all 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 signalling functions.
+'''Oxytocin''' is a [[mammal]]ian hormone involved in the stimulation of smooth muscle contraction that also acts as a neurotransmitter in the [[brain]]. In women, it is released mainly after distension of the [[cervix]] and [[vagina]] during [[labor]], and after stimulation of the nipples, facilitating [[childbirth|birth]] and [[breastfeeding]], respectively.
+==== Opioid peptides ====
+''Opioid peptides'' produced in the body include [[endorphin]]s and [[enkephalin]]s. Opioid peptides act as natural pain killers, or [[opiate]]s, decreasing [[pain]] responses in the central nervous system.
+=== Growth factors ===
+Polypeptide '''growth factors''' control animal cell growth and differentiation. Nerve growth factor (or NGF) is involved in the development and survival of neurons, while platelet-derived growth factor (PDGF) participates in [[blood]] clotting at the site of a wound. PDGF stimulates the spread of [[fibroblast]]s in the vicinity of the clot, facilitating the regrowth of the damaged tissue.
+Given the role of polypeptide growth factors in controlling cell proliferation, abnormalities in growth factor signaling are the basis for a variety of [[disease]]s, including many types of [[cancer]].
-===Vasopressin and oxytocin===
+== Peptides are an important research tool ==
+Peptides have received prominence in [[molecular biology]] in recent times for several reasons:
-* [[Vasopressin]]
+#Peptides allow researchers to generate [[antibody|antibodies]] in animals without the need to purify the protein of interest. The researcher can simply make [[antigen|antigenic]] peptides of sections of the protein.
-* [[Oxytocin]]
+#Peptides have become instrumental in [[mass spectrometry]], allowing the identification of proteins of interest based on peptide masses and sequences.
+#Peptides have recently been used in the study of protein structure and function. For example, synthetic peptides can be used as probes to determine where protein-peptide interactions occur.
+#Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases.
-===The [[Tachykinin peptides]]===
+==Peptide families==
-* [[Substance P]]
+Below is a more detailed list of the major families of ribosomal peptides:
-* [[Kassinin]]
-* [[Neurokinin A]]
-* [[Eledoisin]]
-* [[Neurokinin B]]
-===[[Vasoactive intestinal peptides]]===
+*Vasopressin and oxytocin
-* [[Vasoactive intestinal peptide|VIP]] ''Vasoactive intestinal peptide''
+** [[Vasopressin]]
-* [[PACAP]] ''[[Pituitary adenylate cyclase activating peptide]]''
+** [[Oxytocin]]
-* [[PHI 27]]
-* [[PHM 27]]
-* [[GHRH 1-24]] ''[[Growth hormone releasing hormone 1-24]]''
-* [[Glucagon]]
-* [[Secretin]]
-===[[Pancreatic polypeptide-related peptides]]===
+*The [[Tachykinin peptides]]
-* [[NPY]]
+** [[Substance P]]
-* [[PYY]] ''[[Peptide YY]]''
+** [[Kassinin]]
-* [[Avian pancreatic polypeptide|APP]] ''[[Avian pancreatic polypeptide]]''
+** [[Neurokinin A]]
-* [[HPP]] ''[[Human pancreatic polypeptide]]''
+** [[Eledoisin]]
+** [[Neurokinin B]]
-===[[Opioid peptides]]===
+*[[Vasoactive intestinal peptides]]
-* [[Proopiomelanocortin]] ([[POMC]]) Peptides
+** [[Vasoactive intestinal peptide|VIP]] (''Vasoactive intestinal peptide'')
-* The [[Enkephalin pentapeptides]]
+** [[PACAP]] (''[[Pituitary adenylate cyclase activating peptide]]'')
-* The [[Prodynorphin peptides]]
+** [[PHI 27]]
+** [[PHM 27]]
+** [[GHRH 1-24]] (''[[Growth hormone releasing hormone 1-24]]'')
+** [[Glucagon]]
+** [[Secretin]]
-===Calcitonin peptides===
+*[[Pancreatic polypeptide-related peptides]]
-* [[Calcitonin]]
+** [[NPY]]
-* [[Amylin]]
+** [[PYY]] (''[[Peptide YY]]'')
-*[[AGG01]]
+** [[Avian pancreatic polypeptide|APP]] (''Avian pancreatic polypeptide'')
+** [[HPP]] (''[[Human pancreatic polypeptide]]'')
-==Notes on terminology==
+*[[Opioid peptides]]
-*A ''[[polypeptide]]'' is a single linear chain of amino acids.
+** [[Proopiomelanocortin]] ([[POMC]]) Peptides
-*A ''[[protein]]'' is one or more polypeptides more than about 50 amino acids long.
+** The [[Enkephalin pentapeptides]]
-*An ''[[oligopeptide]]'' or (simply) a ''peptide'' is a polypeptide less than 30-50 amino acids long.
+** The [[Prodynorphin peptides]]
-*A ''[[tripeptide]]'' has three amino acids.
-*A ''[[dipeptide]]'' has two amino acids.
-*A ''[[neuropeptide]]'' is a peptide that is active in association with neural tissue.
-*A ''[[peptide hormone]]'' is a peptide that acts as a [[hormone]].
-==External links==
+*Calcitonin peptides
-*[http://www.peptideresource.com Peptide Resource Page]
+** [[Calcitonin]]
+** [[Amylin]]
+** [[AGG01]]
-==See also==
+==References==
-* [[Peptidomimetic]]s (such as [[peptoid]]s and [[beta-peptide|β-peptide]]s) are molecules related to peptides, but with different properties.
+* Cooper, G. M., and R. E. Hausman. 2004. ''The Cell: A Molecular Approach,'' 3rd edition. Washington, DC: ASM Press & Sunderland, MA: Sinauer Associates. ISBN 0878932143
-* [[Peptide synthesis]]
+* Lodish, H., D. Baltimore, A. Berk, S. L. Zipursky, P. Matsudaira, and J. Darnell. 1996. ''Molecular Cell Biology.'' Oxford: W H Freeman and Company. ISBN 0716727110
-* [[Translation (genetics)|Translation]]
+* Stryer, L. 1995. ''Biochemistry'', 4th edition. New York, NY: W.H. Freeman. ISBN 0716720094
-* [[Ribosome]]
-{{credit|98760524}}
+{{credit7|Peptide|98760524|Peptide_bond|114918900|Peptide_hormone|106998489|Neuropeptide|114698110|Vasopressin|115077827|Opioid_peptide|108943902|Pituitary_gland|114583980}}
 [[Category:Life sciences]]
+[[Category:Biochemistry]]