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. In humans, CoA biosynthesis requires cysteine, pantothenate (vitamin B5), and adenosine triphosphate (ATP).
In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2, which are co-enzymes used in the electron transport chain. It is named as such because the beta carbon of the fatty acid undergoes oxidation to a carbonyl group. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes.
Acyl-CoA dehydrogenases (ACADs) are a class of enzymes that function to catalyze the initial step in each cycle of fatty acid β-oxidation in the mitochondria of cells. Their action results in the introduction of a trans double-bond between C2 (α) and C3 (β) of the acyl-CoA thioester substrate. Flavin adenine dinucleotide (FAD) is a required co-factor in addition to the presence of an active site glutamate in order for the enzyme to function.
Acyl-CoA is a group of coenzymes that metabolize fatty acids. 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 way, fats are converted to ATP, the universal biochemical energy carrier.
The long chain fatty acyl-CoA ligase is an enzyme of the ligase family that activates the oxidation of complex fatty acids. Long chain fatty acyl-CoA synthetase catalyzes the formation of fatty acyl-CoA by a two-step process proceeding through an adenylated intermediate. The enzyme catalyzes the following reaction,
Electron-transferring-flavoprotein dehydrogenase is an enzyme that transfers electrons from electron-transferring flavoprotein in the mitochondrial matrix, to the ubiquinone pool in the inner mitochondrial membrane. It is part of the electron transport chain. The enzyme is found in both prokaryotes and eukaryotes and contains a flavin and FE-S cluster. In humans, it is encoded by the ETFDH gene. Deficiency in ETF dehydrogenase causes the human genetic disease multiple acyl-CoA dehydrogenase deficiency.
Palmitoyl-CoA hydrolase (EC 3.1.2.2) is an enzyme in the family of hydrolases that specifically acts on thioester bonds. It catalyzes the hydrolysis of long chain fatty acyl thioesters of acyl carrier protein or coenzyme A to form free fatty acid and the corresponding thiol:
The human ETFA gene encodes the Electron-transfer-flavoprotein, alpha subunit, also known as ETF-α. Together with Electron-transfer-flavoprotein, beta subunit, encoded by the 'ETFB' gene, it forms the heterodimeric electron transfer flavoprotein (ETF). The native ETF protein contains one molecule of FAD and one molecule of AMP, respectively.
The human ETFB gene encodes the Electron-transfer-flavoprotein, beta subunit, also known as ETF-β. Together with Electron-transfer-flavoprotein, alpha subunit, encoded by the 'ETFA' gene, it forms the heterodimeric Electron transfer flavoprotein (ETF). The native ETF protein contains one molecule of FAD and one molecule of AMP, respectively.
Acyl-CoA thioesterase 2, also known as ACOT2, is an enzyme which in humans is encoded by the ACOT2 gene.
Acyl-coenzyme A thioesterase 4 is an enzyme that in humans is encoded by the ACOT4 gene.
Acyl-coenzyme A thioesterase 11 also known as StAR-related lipid transfer protein 14 (STARD14) is an enzyme that in humans is encoded by the ACOT11 gene. This gene encodes a protein with acyl-CoA thioesterase activity towards medium (C12) and long-chain (C18) fatty acyl-CoA substrates which relies on its StAR-related lipid transfer domain. Expression of a similar murine protein in brown adipose tissue is induced by cold exposure and repressed by warmth. Expression of the mouse protein has been associated with obesity, with higher expression found in obesity-resistant mice compared with obesity-prone mice. Alternative splicing results in two transcript variants encoding different isoforms.
Electron transfer flavoprotein-ubiquinone oxidoreductase, mitochondrial is an enzyme that in humans is encoded by the ETFDH gene. This gene encodes a component of the electron-transfer system in mitochondria and is essential for electron transfer from a number of mitochondrial flavin-containing dehydrogenases to the main respiratory chain.
Acyl-CoA thioesterase 6 is a protein that in humans is encoded by the ACOT6 gene. The protein, also known as C14orf42, is an enzyme with thioesterase activity.
Short-chain acyl-CoA dehydrogenase is an enzyme with systematic name short-chain acyl-CoA:electron-transfer flavoprotein 2,3-oxidoreductase. This enzyme catalyses the following chemical reaction
Medium-chain acyl-CoA dehydrogenase is an enzyme with systematic name medium-chain acyl-CoA:electron-transfer flavoprotein 2,3-oxidoreductase. This enzyme catalyses the following chemical reaction
Very-long-chain acyl-CoA dehydrogenase is an enzyme with systematic name very-long-chain acyl-CoA:electron-transfer flavoprotein 2,3-oxidoreductase. This enzyme catalyses the following chemical reaction
NADH:ubiquinone reductase (non-electrogenic) (EC 1.6.5.9, NDH-2, ubiquinone reductase, coenzyme Q reductase, dihydronicotinamide adenine dinucleotide-coenzyme Q reductase, DPNH-coenzyme Q reductase, DPNH-ubiquinone reductase, NADH-coenzyme Q oxidoreductase, NADH-coenzyme Q reductase, NADH-CoQ oxidoreductase, NADH-CoQ reductase) is an enzyme with systematic name NADH:ubiquinone oxidoreductase. This enzyme catalyses the following chemical reaction:
Acyl-CoA thioesterase 13 is a protein that in humans is encoded by the ACOT13 gene. This gene encodes a member of the thioesterase superfamily. In humans, the protein co-localizes with microtubules and is essential for sustained cell proliferation.
Acyl-CoA thioesterase 1 is a protein that in humans is encoded by the ACOT1 gene.
