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.
Acetoin, also known as 3-hydroxybutanone or acetyl methyl carbinol, is an organic compound with the formula CH3CH(OH)C(O)CH3. It is a colorless liquid with a pleasant, buttery odor. It is chiral. The form produced by bacteria is (R)-acetoin.
Cyanophycin, also known as CGP or multi-L-arginyl-poly, is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups.
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.
The Wood–Ljungdahl pathway is a set of biochemical reactions used by some bacteria. It is also known as the reductive acetyl-coenzyme A (Acetyl-CoA) pathway. This pathway enables these organisms to use hydrogen as an electron donor, and carbon dioxide as an electron acceptor and as a building block for biosynthesis.
Isocitrate lyase, or ICL, is an enzyme in the glyoxylate cycle that catalyzes the cleavage of isocitrate to succinate and glyoxylate. Together with malate synthase, it bypasses the two decarboxylation steps of the tricarboxylic acid cycle and is used by bacteria, fungi, and plants.
Bacterial microcompartments (BMCs) are organelle-like structures found in bacteria. They consist of a protein shell that encloses enzymes and other proteins. BMCs are typically about 40–200 nanometers in diameter and are made entirely of proteins. The shell functions like a membrane, as it is selectively permeable. Other protein-based compartments found in bacteria and archaea include encapsulin nanocompartments and gas vesicles.
2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase (EC 1.1.1.312, 2-hydroxy-4-carboxymuconate 6-semialdehyde dehydrogenase, 4-carboxy-2-hydroxy-cis,cis-muconate-6-semialdehyde:NADP+ oxidoreductase, alpha-hydroxy-gamma-carboxymuconic epsilon-semialdehyde dehydrogenase, 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase, LigC, ProD) is an enzyme with systematic name 4-carboxy-2-hydroxymuconate semialdehyde hemiacetal:NADP+ 2-oxidoreductase. This enzyme catalyses the following chemical reaction
3,4-Dehydroadipyl-CoA semialdehyde dehydrogenase (NADP+) (EC 1.2.1.77, BoxD, 3,4-dehydroadipyl-CoA semialdehyde dehydrogenase) is an enzyme with systematic name 3,4-didehydroadipyl-CoA semialdehyde:NADP+ oxidoreductase. 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
Caffeine dehydrogenase, commonly referred to in scientific literature as caffeine oxidase, is an enzyme with the systematic name caffeine:ubiquinone oxidoreductase. The enzyme is most well known for its ability to directly oxidize caffeine, a type of methylxanthine, to trimethyluric acid. Caffeine dehydrogenase can be found in bacterium Pseudomonas sp. CBB1 and in several species within the genera Alcaligenes, Rhodococcus, and Klebsiella.
The alpha-D-phosphohexomutases are a large superfamily of enzymes, with members in all three domains of life. Enzymes from this superfamily are ubiquitous in organisms from E. Coli to humans, and catalyze a phosphoryl transfer reaction on a phosphosugar substrate. Four well studied subgroups in the superfamily are:
- Phosphoglucomutase (PGM)
- Phosphoglucomutase/Phosphomannomutase (PGM/PMM)
- Phosphoglucosamine mutase (PNGM)
- Phosphoaceytlglucosamine mutase (PAGM)
UDP-N-acetylglucosamine kinase is an enzyme with systematic name ATP:UDP-N-acetyl-alpha-D-glucosamine 3'-phosphotransferase. This enzyme catalyses the following chemical reaction
Propionate kinase is an enzyme with systematic name ATP:propanoate phosphotransferase. This enzyme catalyses the following chemical reaction
UDP-N-acetylglucosamine—undecaprenyl-phosphate N-acetylglucosaminephosphotransferase is an enzyme with systematic name UDP-N-acetyl-alpha-D-glucosamine:ditrans,octacis-undecaprenyl phosphate N-acetyl-alpha-D-glucosaminephosphotransferase. This enzyme catalyses the following chemical reaction
Cyanophycinase (EC 3.4.15.6, cyanophycin degrading enzyme, beta-Asp-Arg hydrolysing enzyme, CGPase, CphB, CphE, cyanophycin granule polypeptidase, extracellular CGPase) is an enzyme. It catalyses the following chemical reaction
3-Fumarylpyruvate hydrolase (EC 3.7.1.20, nagK (gene), naaD (gene)) is an enzyme with systematic name 3-fumarylpyruvate hydrolyase. This enzyme catalyses the following chemical reaction
Cyanophycin synthase (L-aspartate-adding) is an enzyme with systematic name cyanophycin:L-aspartate ligase (ADP-forming). This enzyme catalyses the following chemical reaction
Cyanophycin synthase (L-arginine-adding) is an enzyme with systematic name cyanophycin:L-arginine ligase (ADP-forming). This enzyme catalyses the following chemical reaction:
Azoarcus evansii is a species of bacteria. Its type strain is KB 740T.
