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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.
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 acetyl-CoA enters the citric acid cycle, eventually forming several equivalents of ATP. In this ...
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 Gct family has members that catalyze CoA-transferase reactions, but half of the members do not. They instead catalyze hydrolysis or other reactions involving acyl-CoA.
The following reaction is the oxidation of the fatty acid by FAD to afford an α,β-unsaturated fatty acid thioester of coenzyme A: ACADs can be categorized into three distinct groups based on their specificity for short-, medium-, or long-chain fatty acid acyl-CoA substrates.
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.
coenzyme-A comes in and undergoes hydrogen-atom transfer with the Cys419 radical to generate a coenzyme-A radical. The coenzyme-A radical then picks up the acetyl group from Cys418 to generate acetyl-CoA, leaving behind a Cys418 radical. Pyruvate formate lyase can then undergo radical transfer to put the radical back onto Gly734.
The overall reaction of ACAC(A,B) proceeds by a two-step mechanism. [8] The first reaction is carried out by BC and involves the ATP-dependent carboxylation of biotin with bicarbonate serving as the source of CO 2. The carboxyl group is transferred from biotin to acetyl-CoA to form malonyl-CoA in the second reaction, which is catalyzed by CT.