Acetyl-CoA

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Acetyl-CoA
Acetyl-CoA-2D.svg
Acetyl-CoA-3D-balls.png
Identifiers
CAS number 72-89-9 YesY
PubChem 444493
ChemSpider 392413 YesY
MeSH Acetyl+Coenzyme+A
ChEBI CHEBI:15351 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C23H38N7O17P3S
Molar mass 809.57 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Acetyl coenzyme A or acetyl-CoA is an important molecule in metabolism, used in many biochemical reactions. It is referred to as the "Hub of Metabolism". Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. Structure of coenzyme A (CoASH or CoA) consists of a β-mercaptoethylamine group linked to the vitamin pantothenic acid through an amide linkage. The acetyl group of acetyl-CoA is linked by a "high energy" thioester to the sulfhydryl portion of the β-mercaptoethylamine. It is this thioester bond that makes acetyl-CoA one of the "high energy" compounds. Hydrolysis of the thioester bond is highly exergonic (-31.5 kJ). Acetyl-CoA is produced during breakdown of carbohydrates through glycolysis as well as fatty acid oxidation and 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.

Konrad Bloch and Feodor Lynen were awarded the 1964 Nobel Prize in Physiology and Medicine for their discoveries linking acetyl-CoA and fatty acid metabolism. Fritz Lipmann won the Nobel Prize in 1953 for his discovery of the cofactor Coenzyme A.

Functions[edit]

Pyruvate dehydrogenase and pyruvate formate lyase reactions[edit]

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.

Direct synthesis[edit]

The two components of acetyl-CoA—the acetyl, supplied via acetate, and Coenzyme-A groups—can be linked directly, catalyzed by the enzyme acetyl—CoA synthetase. This process is involved in metabolism of carbon sugars. As a starting point for the citric acid cycle, the acetyl—Co-A synthetase route is less common than the pyruvate dehydrogenase route.

Fatty acid metabolism[edit]

In animals, acetyl-CoA and other acyl-CoA coenzymes are essential 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 very high levels of ketone bodies in the blood, a condition called ketosis, which is different from 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[edit]

Interactive pathway map[edit]

Click on genes, proteins and metabolites below to visit Gene Wiki pages and related Wikipedia articles. The pathway can be downloaded and edited at WikiPathways.

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TCACycle_WP78 go to article go to article go to article go to article go to HMDB go to article go to article go to article Go to article go to article go to article go to article go to article go to article Go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to HMDB go to article go to article go to HMDB go to article go to article go to HMDB go to article go to article go to HMDB go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to WikiPathways go to article go to article go to article go to article
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See also[edit]

References[edit]

  1. ^ Fatland, B. L.; Ke, J; Anderson, MD; Mentzen, WI; Cui, LW; Allred, CC; Johnston, JL; Nikolau, BJ; Wurtele, ES (2002). "Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme a in Arabidopsis". Plant Physiology 130 (2): 740–56. doi:10.1104/pp.008110. PMC 166603. PMID 12376641. 
  2. ^ Fatland, B. L. (2005). "Reverse Genetic Characterization of Cytosolic Acetyl-CoA Generation by ATP-Citrate Lyase in Arabidopsis". The Plant Cell Online 17: 182. doi:10.1105/tpc.104.026211. 

External links[edit]