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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.
These reactions have different functions in cells. The reaction involving acetyl-CoA and butyrate (EC 2.8.3.8), for example, forms butyrate during fermentation. [3] The reaction involving acetyl-CoA and succinate (EC 2.8.3.18) is part of a modified TCA cycle [4] or forms acetate during fermentation. [5]
Structure of acetyl coenzyme A, a thioester that is a key intermediate in the biosynthesis of many biomolecules. Thioesters are common intermediates in many biosynthetic reactions, including the formation and degradation of fatty acids and mevalonate , precursor to steroids.
The medium chain acyl-CoA dehydrogenase (MCAD) is the best known structure of all ACADs, and is the most commonly deficient enzyme within the class that leads to metabolic disorders in animals. [1] This protein is a homotetramer with each subunit containing roughly 400 amino acids and one equivalent of FAD per monomer.
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.
In biochemistry, hydroxymethylglutaryl-CoA synthase or HMG-CoA synthase EC 2.3.3.10 is an enzyme which catalyzes the reaction in which acetyl-CoA condenses with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). This reaction comprises the second step in the mevalonate-dependent isoprenoid biosynthesis pathway.
To participate in specific metabolic processes, fatty acids must first be activated by being joined in thioester linkage (R-CO-SCoA) to the -SH group of coenzyme A, where R is a fatty carbon chain. The thioester bond is a high energy bond. [1] The activation reaction normally occurs in the endoplasmic reticulum or the outer mitochondrial membrane.