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acyl-P + HS-CoA → acyl-S-CoA + P i + H + Three types of acyl-CoA synthases are employed, depending on the chain length of the fatty acid. [3] For example, the substrates for medium chain acyl-CoA synthase are 4-11 carbon fatty acids. [4] The enzyme acyl-CoA thioesterase takes of the acyl-CoA to form a free fatty acid and coenzyme A. [4]
Acyl-CoA synthetases, also known as acyl-CoA ligases, are enzymes that “activate” fatty acids by thioesterification to CoA. [1] It represents the initial step of fatty acid metabolism so that fatty acids can participate in catabolic and anabolic pathways. [ 1 ]
When the enzyme is active, the product, malonyl-CoA, is produced which is a building block for new fatty acids and can inhibit the transfer of the fatty acyl group from acyl-CoA to carnitine with carnitine acyltransferase, which inhibits the beta-oxidation of fatty acids in the mitochondria.
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 ...
The reaction starts when an acyl-CoA (the CoA donor) enters the active site of the enzyme. [7] A glutamate in the active site forms an adduct with acyl-CoA. The acyl-CoA breaks at the thioester bond, forming a CoA and carboxylic acid. The carboxylic acid remains bound to the enzyme, but it is soon displaced by CoA and leaves.
β-oxidation occurs normally until the acyl CoA (because of the presence of a double bond) is not an appropriate substrate for acyl CoA dehydrogenase, or enoyl CoA hydratase: If the acyl CoA contains a cis-Δ 3 bond, then cis-Δ 3-Enoyl CoA isomerase will convert the bond to a trans-Δ 2 bond, which is a regular substrate.
Thus, the two substrates of this enzyme are acetyl-CoA and acyl carrier protein, whereas its two products are CoA and acetyl-acyl-carrier-protein. This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acetyl-CoA:[acyl ...
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.