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 chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. 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 succinate-semialdehyde dehydrogenase (SSADH) (EC 1.2.1.24) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-oxoacid 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, an oxalate 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-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
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 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
In enzymology, a dihydrolipoyllysine-residue succinyltransferase (EC 2.3.1.61) is an enzyme that catalyzes the chemical reaction
In enzymology, a cystathionine gamma-synthase is an enzyme that catalyzes the formation of cystathionine from cysteine and an activated derivative of homoserine, e.g.:
Succinyl-CoA ligase [GDP-forming] subunit alpha, mitochondrial is an enzyme that in humans is encoded by the SUCLG1 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
Succinate-semialdehyde dehydrogenase (NADP+) (EC 1.2.1.79, succinic semialdehyde dehydrogenase (NADP+), succinyl semialdehyde dehydrogenase (NADP+), succinate semialdehyde:NADP+ oxidoreductase, NADP-dependent succinate-semialdehyde dehydrogenase, GabD) is an enzyme with systematic name succinate-semialdehyde:NADP+ oxidoreductase. 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.
