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Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle.All genomes sequenced to date encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it (or a thioester) as a substrate.
Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. [2] Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.
Acetyl-CoA carboxylase (ACC) is a biotin-dependent enzyme (EC 6.4.1.2) that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase (BC) and carboxyltransferase (CT).
Pymol-generated image of E1 subunit of pyruvate dehydrogenase complex in E. Coli. The E1 subunit, called the pyruvate dehydrogenase subunit, is either a homodimer (comprising two “α” chains, e.g. in Escherichia coli) or a heterotetramer of two different chains (two “α” and two “β” chains).
General chemical structure of an acyl-CoA, where R is a carboxylic acid side chain. Acyl-CoA is a group of CoA-based coenzymes that metabolize carboxylic acids. Fatty acyl-CoA's are susceptible to beta oxidation, forming, ultimately, acetyl-CoA.
The CitF family catalyzes reactions involving acetyl-CoA and citrate EC 2.8.3.10), but its main role is as an acyl-ACP transferase (as part of citrate lyase; EC 4.1.3.6). The MdcA family catalyzes reactions involving acetyl-CoA and malonate (EC 2.8.3.3), but it too is an acyl-ACP transferase (as part of malonate decarboxylase; EC 4.1.1.9).
The role of the ACS enzyme is to combine acetate and Coenzyme A to form acetyl-CoA, however its significance is much larger. The most well known function of the product from this enzymatic reaction is the use of acetyl-CoA in the role of the TCA cycle as well as in the production of fatty acid.
Three examples of these reactions are the activity of coenzyme A (CoA) transferase, which transfers thiol esters, [3] the action of N-acetyltransferase, which is part of the pathway that metabolizes tryptophan, [4] and the regulation of pyruvate dehydrogenase (PDH), which converts pyruvate to acetyl CoA. [5]