Acetyl-CoA
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225337969
2008-07-13T04:24:36Z
Bform
4183934
/* Other reactions */ added info regarding acetylation as post translational modification. And removed redundacy relating to hmgcoa/cholesterol
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| ImageFile = Acetyl-CoA-2D.svg
| ImageSize = 350px
| ImageFile2 = Acetyl-CoA-3D-balls.png
| IUPACName =
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| Section1 = {{Chembox Identifiers
| CASNo = 72-89-9
| PubChem = 181
| SMILES = O=C(NCCSC(=O)C)CCNC<br>(=O)[C@H](O)C(C)(C) COP(=O)(O)OP(=O)<br>(O)OC[C@H]1O[C@H] ([C@H](O)[C@@H]1OP(=O)<br>(O)O)n1cnc2c(N)ncnc12
| MeSHName = Acetyl+Coenzyme+A
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>23</sub>H<sub>38</sub>N<sub>7</sub>O<sub>17</sub>P<sub>3</sub>S
| MolarMass = 809.572
| Appearance =
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| Section3 = {{Chembox Hazards
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}}
'''Acetyl-CoA''' is an important molecule in metabolism, used in many biochemical reactions. Its main use is to convey the [[carbon]] [[atom]]s within the [[acetyl]] group to the [[citric acid cycle]] to be [[oxidation|oxidized]] for energy production. In chemical structure, acetyl-CoA is the [[thioester]] between [[coenzyme A]] (a [[thiol]]) and [[acetic acid]] (an [[acyl]] group carrier). Acetyl-CoA is produced during the second step of aerobic [[cellular respiration]], [[pyruvate decarboxylation]], which occurs in the [[Matrix (biology)|matrix]] of the [[mitochondria]]. Acetyl-CoA then enters the citric acid cycle.
Acetyl-CoA is also an important component in the biogenic synthesis of the neurotransmitter [[acetylcholine]]. [[Choline]], in combination with Acetyl-CoA, is catalyzed by the enzyme [[choline acetyltransferase]] to produce acetylcholine and a [[coenzyme a]] byproduct.
==Functions==
===Pyruvate dehydrogenase and pyruvate formate lyase reactions===
The oxidative conversion of [[pyruvate]] into acetyl-CoA is referred to as the '''pyruvate dehydrogenase reaction'''. It is catalyzed by the [[pyruvate dehydrogenase complex]]. Other conversions between pyruvate and acetyl-CoA are possible. For example, [[pyruvate formate lyase]] disproportionates pyruvate into acetyl-CoA and [[formic acid]]. The pyruvate formate lyase reaction does not involve any net oxidation or reduction.
===Fatty acid metabolism===
In animals, acetyl-CoA is very central to the balance between [[carbohydrate metabolism]] and [[fat]] metabolism (see [[fatty acid synthesis]]). In normal circumstances, acetyl-CoA from fatty acid metabolism feeds into the [[citric acid cycle]], contributing to the cell's energy supply. In the [[liver]], when levels of circulating fatty acids are high, the production of acetyl-CoA from fat breakdown exceeds the cellular energy requirements. To make use of the energy available from the excess acetyl-CoA, [[ketone bodies]] are produced which can then circulate in the blood.
In some circumstances, this can lead to the presence of ketone bodies in the [[blood]], a condition called [[ketosis]]. Benign dietary ketosis can safely occur in people following [[low-carbohydrate diet]]s, which cause fats to be metabolised as a major source of energy. This is different from [[ketosis]] brought on as a result of starvation and [[ketoacidosis]], a dangerous condition that can affect [[diabetics]].
In plants, de novo fatty acid synthesis occurs in the plastids. Many seeds accumulate large reservoirs of seed oils to support [[germination]] and early growth of the seedling before it is a net photosynthetic organism. Fatty acids are incorporated into membrane lipids, the major component of most membranes.
===Other reactions===
* Two acetyl-CoA can be [[Condensation reaction|condensed]] to create [[acetoacetyl-CoA]], the first step in the HMG-CoA/ [[mevalonic acid pathway]] leading to synthesis of [[isoprenoid]]s. In animals HMG-CoA is a vital precursor to [[cholesterol]] and [[Ketone bodies|ketone]] synthesis.
* Acetyl-CoA is also the source of the acetyl group incorporated onto certain lysine residues of histone and non-histone proteins in the post-translational modification [[acetylation]], a reaction catalyzed by [[acetyltransferases]].
* In plants and animals, cytosolic acetyl-CoA is synthesized by [[ATP citrate lyase]] [http://www.plantphysiol.org/cgi/content/full/130/2/740]. When glucose is abundant in the blood of animals, it is converted via [[glycolysis]] in the [[cytosol]] to [[pyruvate]], and thence to acetyl-CoA in the mitochondrion. The excess of [[acetyl-CoA]] results in production of excess [[citrate]], which is exported into the cytosol to give rise to cytosolic acetyl-CoA.
* Acetyl-CoA can be [[carboxylated]] in the cytosol by [[acetyl-CoA carboxylase]], giving rise to [[malonyl-CoA]], a substrate required for synthesis of flavonoids and related polyketides, for elongation of fatty acids to produce waxes, [[cuticle]], and seed oils in members of the [[Brassica]] family, and for malonation of proteins and other phytochemicals [http://www.plantcell.org/cgi/content/full/17/1/182].
* In plants, these include [[sesquiterpene]]s, [[brassinosteroid]]s (hormones), and membrane [[sterol]]s.
== See also ==
* [[Citric acid cycle]]
* [[HMG-CoA reductase pathway]]
* [[Fatty acid metabolism]]
* [[Acyl CoA]]
* [[Acetyl Co-A synthetase]]
* [[Malonyl-CoA decarboxylase]]
==External links==
* {{MeshName|Acetyl+Coenzyme+A}}
{{Cholesterol metabolism intermediates}}
[[Category:Metabolism]]
[[Category:Thioesters]]
[[Category:Coenzymes]]
[[cs:Acetyl-CoA]]
[[de:Coenzym A#Acetyl-CoA]]
[[es:Acetil-CoA]]
[[eo:Acetila Koenzimo A]]
[[fr:Acétyl-coenzyme A]]
[[it:Acetil-coenzima A]]
[[he:אצטיל קואנזים A]]
[[lb:HSCoA]]
[[hu:Acetil-koenzim A]]
[[nl:Acetyl-CoA]]
[[ja:アセチルCoA]]
[[pt:Acetilcoenzima A]]
[[fi:Asetyylikoentsyymi-A]]
[[sv:Acetyl-CoA]]
[[tr:Asetil CoA]]
[[zh:乙酰辅酶A]]