Acyl-CoA

Acyl-CoA

Acyl-CoA is a coenzyme involved in the metabolism of fatty acids. It is a temporary compound formed when coenzyme A (CoA) attaches to the end of a long-chain fatty acid, inside living cells. The CoA is then removed from the chain, carrying two carbons from the chain with it, forming acetyl-CoA. This is then used in the citric acid cycle to start a chain of reactions, eventually forming many adenosine triphosphate.

Functions

Fatty acid activation

To be oxidatively degraded, a fatty acid must first be activated in a two-step reaction catalyzed by acyl-CoA synthetase. First, the fatty acid displaces the diphosphate group of ATP, then coenzyme A (HSCoA) displaces the AMP group to form an Acyl-CoA. The acyladenylate product of the first step has a large free energy of hydrolysis and conserves the free energy of the cleaved phosphoanhydride bond in ATP. The second step, transfer of the acyl group to CoA (the same molecule that carries acetyl groups as acetyl-CoA), conserves free energy in the formation of a thioester bond. Consequently, the overall reaction

Fatty acid + CoA + ATP <=> Acyl-CoA + AMP + PPi

has a free energy change near zero. Subsequent hydrolysis of the product PPi (by the enzyme inorganic pyrophosphatase) is highly exergonic, and this reaction makes the formation of acyl-CoA spontaneous and irreversible.

Fatty acids are activated in the cytosol, but oxidation occurs in the mitochondria. Because there is no transport protein for CoA adducts, acyl groups must enter the mitochondria via a shuttle system involving the small molecule carnitine. [ Pratt C.W., Cornely, K. "Essential Biochemistry". John Wiley & Sons, Inc. (2004) ]

ee also

* Acetyl-CoA
* Coenzyme A
* Acyl CoA dehydrogenase
* Fatty acid metabolism

References

*1. Pratt C.W., Cornely K. "Essential Biochemistry". John Wiley & Sons, Inc. (2004)

External links

*


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См. также в других словарях:

  • Acyl-CoA — Strukturmodell des Coenzym A. Strukturformel von Coenzym A. Coenzym A (auch Koenzym A, kurz CoA oder CoASH) ist ein Coenzym, das zur „Aktivierung“ von Alkansäuren und deren …   Deutsch Wikipedia

  • acyl-CoA — Condensation product of a carboxylic acid and coenzyme A; metabolic intermediate of importance, notably in the oxidation and synthesis of fat. SYN: acyl coenzyme A. acyl CoA dehydrogenase (NADPH) …   Medical dictionary

  • acyl CoA — ac·yl CoA (aґsəl ko aґ) acyl coenzyme A …   Medical dictionary

  • Acyl CoA dehydrogenase — is the enzyme used to catalyze the first step of β oxidation in Fatty acid metabolism. ReactionThe following reaction is the oxidation of the fatty acid by FAD.The enzyme catalyzes the formation of a double bond between the C 2 and C 3. The end… …   Wikipedia

  • acyl-CoA desaturase — acyl CoA de·sat·ur·ase (aґsəl ko aґ de sachґə rās) stearoyl CoA 9 desaturase …   Medical dictionary

  • Acyl-CoA hydrolase — In enzymology, an acyl CoA hydrolase (EC number|3.1.2.20) is an enzyme that catalyzes the chemical reaction:acyl CoA + H2O ightleftharpoons CoA + a carboxylateThus, the two substrates of this enzyme are acyl CoA and H2O, whereas its two products… …   Wikipedia

  • Acyl-CoA dehydrogenase (NADP+) — In enzymology, an acyl CoA dehydrogenase (NADP+) (EC number|1.3.1.8) is an enzyme that catalyzes the chemical reaction:acyl CoA + NADP+ ightleftharpoons 2,3 dehydroacyl CoA + NADPH + H+Thus, the two substrates of this enzyme are acyl CoA and… …   Wikipedia

  • Acyl-CoA oxidase — In enzymology, an acyl CoA oxidase (EC number|1.3.3.6) is an enzyme that catalyzes the chemical reaction:acyl CoA + O2 ightleftharpoons trans 2,3 dehydroacyl CoA + H2O2Thus, the two substrates of this enzyme are acyl CoA and O2, whereas its two… …   Wikipedia

  • acyl CoA synthetase — ac·yl CoA syn·the·tase (aґsəl ko aґ sinґthə tās) 1. any enzyme of the ligase class that catalyzes the formation of an activated acyl coenzyme A thioester; individual enzymes are specific for a range of fatty acid chain lengths. See …   Medical dictionary

  • acyl-CoA dehydrogenase — ac·yl CoA de·hy·dro·gen·ase (aґsəl ko aґ de hiґdro jən ās) [EC 1.3.99.3] any of several enzymes of the oxidoreductase class that catalyze the oxidation of acyl coenzyme A thioesters to the enoyl coenzyme A form, using a flavin… …   Medical dictionary


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