The citric acid cycle—also known as the Krebs cycle, Szent-Györgyi-Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of biochemical reactions to release the energy stored in nutrients through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The chemical energy released is available under the form of ATP. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism. Even though it is branded as a 'cycle', it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.
Succinyl-coenzyme A, abbreviated as succinyl-CoA or SucCoA, is a thioester of succinic acid and coenzyme A.
Succinyl coenzyme A synthetase is an enzyme that catalyzes the reversible reaction of succinyl-CoA to succinate. The enzyme facilitates the coupling of this reaction to the formation of a nucleoside triphosphate molecule from an inorganic phosphate molecule and a nucleoside diphosphate molecule. It plays a key role as one of the catalysts involved in the citric acid cycle, a central pathway in cellular metabolism, and it is located within the mitochondrial matrix of a cell.
In enzymology, a 3-oxoacid CoA-transferase 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 citramalate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, an oxalate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, a succinate-hydroxymethylglutarate CoA-transferase is an enzyme that catalyzes the chemical reaction
In enzymology, a succinyl-CoA:(R)-benzylsuccinate CoA-transferase is an enzyme that catalyzes the chemical reaction
The enzyme citramalyl-CoA lyase 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
The enzyme itaconyl-CoA hydratase (EC 4.2.1.56) catalyzes the chemical reaction
The enzyme succinyl-CoA hydrolase (EC 3.1.2.3) catalyzes the reaction
In enzymology, a 3-oxoadipyl-CoA thiolase 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.
Succinyl-CoA:3-oxoacid CoA transferase deficiency is an inborn error of ketone body utilization. Succinyl-CoA:3-oxoacid CoA transferase catalyzes the transfer of coenzyme A from succinyl-coenzyme A to acetoacetate. It can be caused by mutation in the OXCT1 gene.
Succinate-semialdehyde dehydrogenase (acylating) (EC 1.2.1.76, succinyl-coA reductase, coenzyme-A-dependent succinate-semialdehyde dehydrogenase) is an enzyme with systematic name succinate semialdehyde:NADP+ oxidoreductase (CoA-acylating). This enzyme catalyses the following chemical reaction
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.
