Ацетил-КоА: структура, функции и метаболизм

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| Name = Acetyl CoA
| ImageFile = Acetyl CoA 2D colored. svg
| ImageSize = 320
| ImageFile2 = Acetyl CoA 3D balls. png
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| ImageFile3 = Acetyl CoA 3D vdW. png
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| PIN = O1 {(3R) 4 [(3 {[2 (Acetylsulfanyl)ethyl]amino} 3 oxopropyl)amino] 3 hydroxy 2,2 dimethyl 4 oxobutyl} O3 {[(2R,3S,4R,5R) 5 (6 amino 9H purin 9 yl) 4 hydroxy 3 (phosphonooxy)oxolan 2 yl]methyl} dihydrogen diphosphate
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| Section2 = Chembox Properties
| C=23 | H=38 | N=7 | O=17 | P=3 | S=1
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| LambdaMax = 260 nm; 232 nm
| Absorbance = ε260 = 16.4 mM−1 cm−1 (adenosine) Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. Coenzyme A (CoASH or CoA) consists of a β mercaptoethylamine group linked to pantothenic acid (vitamin B5) through an amide linkage and 3' phosphorylated ADP. The acetyl group (indicated in blue in the structural diagram on the right) of acetyl CoA is linked to the sulfhydryl substituent of the β mercaptoethylamine group. This thioester linkage is a "high energy" bond, which is particularly reactive. Hydrolysis of the thioester bond is exergonic (−31.5 kJ/mol). CoA is acetylated to acetyl CoA by the breakdown of carbohydrates through glycolysis and by the breakdown of fatty acids through β oxidation. Acetyl CoA then enters the citric acid cycle, where the acetyl group is oxidized to carbon dioxide and water, and the energy released is captured in the form of 11 ATP and one GTP per acetyl group. Konrad Bloch and Feodor Lynen were awarded the 1964 Nobel Prize in Physiology or 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.

Acetyl CoA is a metabolic intermediate that is involved in many metabolic pathways in an organism. It is produced during the breakdown of glucose, fatty acids, and amino acids, and is used in the synthesis of many other biomolecules, including cholesterol, fatty acids, and ketone bodies. Acetyl CoA is also a key molecule in the citric acid cycle, which is a series of chemical reactions that occur in the mitochondria of cells and is responsible for generating energy in the form of ATP. In addition, acetyl CoA is a precursor for the biosynthesis of various acetyl chemicals, acting as an intermediate to transfer an acetyl group during the biosynthesis of those acetyl chemicals. Acetyl CoA is also involved in the regulation of various cellular mechanisms by providing acetyl groups to target amino acid residues for post translational acetylation reactions of proteins.

The acetylation of CoA is determined by the carbon sources.

At high glucose levels, acetyl CoA is produced through glycolysis. Pyruvate undergoes oxidative decarboxylation in which it loses its carboxyl group (as carbon dioxide) to form acetyl CoA, giving off 33.5 kJ/mol of energy. 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. At low glucose levels, the production of acetyl CoA is linked to β oxidation of fatty acids. Fatty acids are first converted to acyl CoA. Acyl CoA is then degraded in a four step cycle of oxidation, hydration, oxidation and thiolysis catalyzed by four respective enzymes, namely acyl CoA dehydrogenase, enoyl CoA hydratase, 3 hydroxyacyl CoA dehydrogenase, and thiolase. The cycle produces a new fatty acid chain with two fewer carbons and acetyl CoA as a byproduct.

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.