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).
Acetyl-CoA is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle to be oxidized for energy production. Coenzyme A consists of a β-mercaptoethylamine group linked to the vitamin pantothenic acid (B5) through an amide linkage and 3'-phosphorylated ADP. The acetyl group of acetyl-CoA is linked to the sulfhydryl substituent of the β-mercaptoethylamine group. This thioester linkage is a "high energy" bond, which is particularly reactive. Hydrolysis of the thioester bond is exergonic (−31.5 kJ/mol).
Succinyl-coenzyme A, abbreviated as succinyl-CoA or SucCoA, is a thioester of succinic acid and coenzyme A.
The branched-chain α-ketoacid dehydrogenase complex is a multi-subunit complex of enzymes that is found on the mitochondrial inner membrane. This enzyme complex catalyzes the oxidative decarboxylation of branched, short-chain alpha-ketoacids. BCKDC is a member of the mitochondrial α-ketoacid dehydrogenase complex family comprising pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key enzymes that function in the Krebs cycle.
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,
Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are enzymes which convert two units of acetyl-CoA to acetoacetyl CoA in the mevalonate pathway.
In enzymology, an acetoacetyl-CoA reductase (EC 1.1.1.36) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-methyl-2-oxobutanoate dehydrogenase (EC 1.2.4.4) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-oxoadipate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, an acetate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, a succinate-citramalate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, a succinate-CoA ligase (ADP-forming) is an enzyme that catalyzes the chemical reaction
In enzymology, a succinate—CoA ligase (GDP-forming) is an enzyme that catalyzes the chemical reaction
In enzymology, an acetyl-CoA C-acetyltransferase is an enzyme that catalyzes the chemical reaction
In molecular biology, 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. HMG-CoA is an intermediate in both cholesterol synthesis and ketogenesis. This reaction is overactivated in patients with diabetes mellitus type 1 if left untreated, due to prolonged insulin deficiency and the exhaustion of substrates for gluconeogenesis and the TCA cycle, notably oxaloacetate. This results in shunting of excess acetyl-CoA into the ketone synthesis pathway via HMG-CoA, leading to the development of diabetic ketoacidosis.
In enzymology, a propionyl-CoA C2-trimethyltridecanoyltransferase is an enzyme that catalyzes the chemical reaction
3-oxoacid CoA-transferase 1 (OXCT1) is an enzyme that in humans is encoded by the OXCT1 gene. It is also known as succinyl-CoA-3-oxaloacid CoA transferase (SCOT). Mutations in the OXCT1 gene are associated with succinyl-CoA:3-oxoacid CoA transferase deficiency. This gene encodes a member of the 3-oxoacid CoA-transferase gene family. The encoded protein is a homodimeric mitochondrial matrix enzyme that plays a central role in extrahepatic ketone body catabolism by catalyzing the reversible transfer of coenzyme A (CoA) from succinyl-CoA to acetoacetate.
In organic chemistry, keto acids or ketoacids are organic compounds that contain a carboxylic acid group and a ketone group. In several cases, the keto group is hydrated. The alpha-keto acids are especially important in biology as they are involved in the Krebs citric acid cycle and in glycolysis.
Coenzyme A transferases (CoA-transferases) are transferase enzymes that catalyze the transfer of a coenzyme A group from an acyl-CoA donor to a carboxylic acid acceptor. Among other roles, they are responsible for transfer of CoA groups during fermentation and metabolism of ketone bodies. These enzymes are found in all three domains of life.
