The glyoxylate cycle, a variation of the tricarboxylic acid cycle, is an anabolic pathway occurring in plants, bacteria, protists, and fungi. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of carbohydrates.[1] In microorganisms, the glyoxylate cycle allows cells to use two carbons (C2 compounds), such as acetate, to satisfy cellular carbon requirements when simple sugars such as glucose or fructose are not available.[2] The cycle is generally assumed to be absent in animals, with the exception of nematodes at the early stages of embryogenesis. In recent years, however, the detection of malate synthase (MS) and isocitrate lyase (ICL), key enzymes involved in the glyoxylate cycle, in some animal tissue has raised questions regarding the evolutionary relationship of enzymes in bacteria and animals and suggests that animals encode alternative enzymes of the cycle that differ in function from known MS and ICL in non-metazoan species.[1][3]
Plants as well as some algae and bacteria can use acetate as the carbon source for the production of carbon compounds. Plants and bacteria employ a modification of the TCA cycle called the glyoxylate cycle to produce four carbon dicarboxylic acid from two carbon acetate units. The glyoxylate cycle bypasses the two oxidative decarboxylation reactions of the TCA cycle and directly converts isocitrate through isocitrate lyase and malate synthase into malate and succinate.
The glyoxylate cycle was discovered in 1957 at the University of Oxford by Sir Hans Kornberg and his mentor Hans Krebs, resulting in a Nature paper Synthesis of Cell Constituents from C2-Units by a Modified Tricarboxylic Acid Cycle.[4]
^ abKondrashov FA, Koonin EV, Morgunov IG, Finogenova TV, Kondrashova MN (October 2006). "Evolution of glyoxylate cycle enzymes in Metazoa: evidence of multiple horizontal transfer events and pseudogene formation". Biology Direct. 1: 31. doi:10.1186/1745-6150-1-31. PMC 1630690. PMID 17059607.
^Lorenz MC, Fink GR (October 2002). "Life and death in a macrophage: role of the glyoxylate cycle in virulence". Eukaryotic Cell. 1 (5): 657–62. doi:10.1128/EC.1.5.657-662.2002. PMC 126751. PMID 12455685.
^Popov, EA; Moskalev, EA; Shevchenko, MU; Eprintsev, AT (November 2005). "Comparative analysis of glyoxylate cycle key enzyme isocitrate lyase from organisms of different systematic groups". Journal of Evolutionary Biochemistry and Physiology. 41 (6): 631–639. doi:10.1007/s10893-006-0004-3. S2CID 30856607.
^Kornberg, H. L.; Krebs, H. A. (1957). "Synthesis of Cell Constituents from C 2 -Units by a Modified Tricarboxylic Acid Cycle". Nature. 179 (4568): 988–991. Bibcode:1957Natur.179..988K. doi:10.1038/179988a0. ISSN 1476-4687. PMID 13430766. S2CID 40858130.
The glyoxylatecycle, a variation of the tricarboxylic acid cycle, is an anabolic pathway occurring in plants, bacteria, protists, and fungi. The glyoxylate...
carbohydrates. The glyoxylatecycle is also important for induction of plant defense mechanisms in response to fungi. The glyoxylatecycle is initiated through...
gluconeogenesis, the urea cycle, the glyoxylatecycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle. Oxaloacetic acid undergoes...
appear to have converged to the TCA cycle. Calvin cycleGlyoxylatecycle Reverse (reductive) Krebs cycle Krebs cycle (simple English) Lowenstein JM (1969)...
the presence of a glyoxylatecycle (also known as glyoxylate shunt) to produce four-carbon dicarboxylic acid precursors. The glyoxylate shunt comprises...
a product of the glyoxylatecycle, which converts two two-carbon acetyl units into the four-carbon succinate. The glyoxylatecycle is utilized by many...
1), or ICL, is an enzyme in the glyoxylatecycle that catalyzes the cleavage of isocitrate to succinate and glyoxylate. Together with malate synthase,...
Glyoxylate and dicarboxylate metabolism describes a variety of reactions involving glyoxylate or dicarboxylates. Glyoxylate is the conjugate base of glyoxylic...
acetyl-CoA + H2O + glyoxylate → {\displaystyle \rightarrow } (S)-malate + CoA The 3 substrates of this enzyme are acetyl-CoA, H2O, and glyoxylate, whereas its...
additionally the key enzymes of the glyoxylatecycle (isocitrate lyase and malate synthase) which accomplish the glyoxylatecycle bypass. Thus, glyoxysomes (as...
The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). Animals that use...
succinate and pyruvate. The methylcitrate cycle is closely related to both the citric acid cycle and the glyoxylatecycle, in that they share substrates, enzymes...
Glyoxylate reductase (EC 1.1.1.26), first isolated from spinach leaves, is an enzyme that catalyzes the reduction of glyoxylate to glycolate, using the...
: 571 Examples of amphibolic pathways are the citric acid cycle and the glyoxylatecycle. These sets of chemical reactions contain both energy producing...
cholesterol synthesis in animals. Other peroxisomal functions include the glyoxylatecycle in germinating seeds ("glyoxysomes"), photorespiration in leaves, glycolysis...
NADH and FADH2 (for example produced during glycolysis and the citric acid cycle) to establish an electrochemical gradient (often a proton gradient) across...
formed.[citation needed] The citric acid cycle is also called the Krebs cycle or the tricarboxylic acid cycle. When oxygen is present, acetyl-CoA is produced...
reactions lead to the formation of glyoxylate which will thus become part of the second cycle. In the second cycle, glyoxylate is approximately one equivalent...
metabolism. He discovered the urea cycle and later, working with Hans Kornberg, the citric acid cycle and the glyoxylatecycle. Modern biochemical research...
decarboxylation. The resulting acetyl-CoA enters the citric acid cycle (or Krebs Cycle), where the acetyl group of the acetyl-CoA is converted into carbon...
two ATPs is formed in the glycolysis cycle. The glycolysis pathway is later associated with the Citric Acid Cycle which produces additional equivalents...
suggested that a nonenzymatic precursor to the Krebs cycle, glyoxylatecycle, and reverse Krebs cycle might have originated, where oxidation and reduction...
normal conditions, acetyl-CoA is further oxidized by the citric acid cycle (TCA/Krebs cycle) and then by the mitochondrial electron transport chain to release...
peroxisomal functions, glyoxysomes also possess the key enzymes of the Glyoxylatecycle. Microbodies were first discovered and named in 1954 by Rhodin. Two...
needed] from the folk song. The melody is used in Harold Baum's "The GlyoxylateCycle" in The Biochemists' Songbook, and in the 1950 novelty song "The Thing"...
storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose...
host cell for the parasite) such that it cannot sustain the parasitic life cycle long enough for productive growth. G6PD deficiency – A hereditary disease...
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