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| − | '''Пептиды''' (греч. πεπτος - питательный) - семейство веществ, [[молекулы]] которых построены из остатков α-аминокислот, соединённых в цепь [[Пептидная связь|пептидными (амидными) связями]] '''-C(O)NH-'''. | + | '''Полипептиды''' (син.: '''полимиксины''') - группа бактерицидных [[антибиотики|антибиотиков]], обладающих узким спектром активности против грамотрицательной флоры. Основное клиническое значение имеет активность полимиксинов в отношении P.aeruginosa. |
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| − | Это природные или синтетические соединения, содержащие десятки, сотни или тысячи [[мономеры|мономерных звеньев]] — [[аминокислоты|аминокислот]]. Полипептиды состоят из сотен аминокислот, в противоположность [[олигопептиды|олигопептидам]], состоящим из небольшого числа аминокислот (не более 10-50), и простым пептидам (до 10).
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| − | *Полипептиды могут иметь в молекуле неаминокислотные фрагменты, например углеводные остатки.
| + | {{Антибиотики разных групп}} |
| − | *Природные полипептиды с [[молекулярная масса|молекулярной массой]] более 6000 [[дальтон]] называют [[Белки|белками]].
| + | {{Антибиотики}} |
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| − | ==Олигопептиды и полипептиды==
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| − | Грань между олигопептидами и полипептидами (тот размер, при котором белковая молекула перестаёт считаться олигопептидом и становится полипептидом) достаточно условна. Часто пептиды, содержащие менее 10-20 аминокислотных остатков, называют олигопептидами, а вещества с большим числом аминокислотных звеньев - полипептидами. Во многих случаях эта грань в научной литературе не проводится вообще и небольшая белковая молекула (такая, как [[окситоцин]]) упоминается как полипептид (или просто как пептид).
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| − | ==История==
| + | {{drug-stub}} |
| − | Пептиды впервые были выделены из гидролизатов белков, полученных с помощью ферментирования.
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| − | *Термин '''пептид''' предложен Э. [[Фишер]]ом, который к 1905 г. разработал общий метод синтеза пептидов.
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| − | В 1953 В. [[Дю Виньо]] синтезировал [[окситоцин]], первый полипептидный [[гормон]]. В 1963 г., на основе концепции твердофазного пептидного синтеза (P. [[Меррифилд]]) были созданы автоматические синтезаторы пептидов.
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| − | Использование методов синтеза полипептидов позволило получить синтетический [[инсулин]] и др. [[ферменты]].
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| − | The distinction is that peptides are short and polypeptides proteins are long. There are several different conventions to determine these, all of which have flaws.
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| − | 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.
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| − | 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. Long peptides, such as the [[amyloid beta|amyloid beta peptide]] linked to [[Alzheimer's disease]], can be considered proteins; and small proteins, such as [[insulin]], can be considered 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.
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| − | ==Peptide classes==
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| − | Here are the major classes of peptides, according to how they are produced:
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| − | ; Ribosomal peptides : Are synthesized by [[Translation (biology)|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 those utilized by the ribosome, 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).
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| − | ; [[Nonribosomal peptide]]s : Are synthesized using a [[Modularity (biology)|modular]] enzyme complex (which functions much like a conveyor belt on a factory). Nonribosomal peptides 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 diverse 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.
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| − | ; 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.
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| − | ; Peptones : Are derived from animal meat digested by proteolases. The resulting material is used as a source of proteins in nutrient media for growing bacteria and fungi.
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| − | ; 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.
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| − | == Peptides in Molecular Biology ==
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| − | 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.
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| − | Another reason is that peptides have become instrumental in [[mass spectrometry]], allowing the identification of proteins of interest based on peptide masses and sequence.
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| − | 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.
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| − | Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases.
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| − | ==Известные "семейства" пептидов==
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| − | Семейства пептидов в этом разделе являются рибосомальными, обычно они обладают гормональной активностью. <!--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.
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| − | ===Vasoactive intestinal peptides===
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| − | * [[Vasoactive intestinal peptide|VIP]] ''Vasoactive intestinal peptide''
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| − | * [[PACAP]] ''[[Pituitary adenylate cyclase activating peptide]]''
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| − | * [[PHI 27]]
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| − | * [[PHM 27]]
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| − | * [[GHRH 1-24]] ''[[Growth hormone releasing hormone 1-24]]''
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| − | * [[Glucagon]]
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| − | * [[Secretin]]
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| − | ===Pancreatic polypeptide-related peptides===
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| − | * [[NPY]]
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| − | * [[PYY]] ''[[Peptide YY]]''
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| − | * [[Avian pancreatic polypeptide|APP]] ''[[Avian pancreatic polypeptide]]''
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| − | * [[HPP]] ''[[Human pancreatic polypeptide]]''
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| − | ===Calcitonin peptides===
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| − | * [[Calcitonin]]
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| − | * [[Amylin]]
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| − | *[[AGG01]]
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| − | * [[Peptidomimetic]]s (such as [[peptoid]]s and [[beta-peptide|β-peptide]]s) are molecules related to peptides, but with different properties.
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| − | * [[Peptide synthesis]]
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| − | * [[Translation (genetics)|Translation]]
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| − | {{Peptides}}
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| − | *''[[]]'' are one or more polypeptides more than about 50 amino acids long.
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| − | ===Опиоидные пептиды===
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| − | * [[:en:Proopiomelanocortin]] ([[POMC]]) Peptides
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| − | * [[:en:Enkephalin pentapeptides]]
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| − | * [[:en:Prodynorphin peptides]]
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| − | ===Пептиды (Tachykinin peptides)===
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| − | * [[:en:Substance P]]
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| − | * [[:en:Kassinin]]
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| − | * [[Нейрокинин А]], [[:en:Neurokinin A]]
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| − | * [[:en:Eledoisin]]
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| − | * [[Нейрокинин В]], [[:en:Neurokinin B]]
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| − | ==Терминология по теме==
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| − | * ''[[Полипептиды]]'' простая линейная цепь, состоящая из аминокислот
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| − | * ''[[Олигопептиды]]'' или (просто) ''пептиды'' - полипептиды с числом аминокислот в цепи до 30-50
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| − | * ''[[Дипептиды]]''
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| − | * ''[[Трипептиды]]''
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| − | * ''[[Пентапептиды]]''
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| − | * ''[[Нейропептиды]]'' пептиды, ассоциированные с нервной тканью
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| − | * ''[[Пептидные гормоны]]'' - петиды с [[Гормон]]альной активностью
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| − | ==См. также==
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| − | * [[Белки]]
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| − | * [[Пептиды]]
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| − | * [[Аминокислоты]]
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| − | * [[Рибосома]]
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| − | ==Внешние ссылки==
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| − | *[http://forum.xumuk.ru/index.php?showtopic=145 Полипептиды] (специализированная ветвь форума ХИМИК)
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| − | [[Категория:Белки]]
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| − | [[Категория:Аминокислоты| ]]
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| − | [[Category:Биохимия]]
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