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ATP citrate lyase catalyses the Mg.ATP-dependent, CoA-dependent cleavage of citrate into oxaloacetate and acetyl-CoA, a key step in the reductive tricarboxylic acid pathway of CO 2 assimilation used by a variety of autotrophic bacteria and archaea to fix carbon dioxide. [4] ATP citrate lyase is composed of two distinct subunits.
The Dieckmann condensation, where a molecule with two ester groups reacts intramolecularly, forming a cyclic β-keto ester. In this case, the ring formed must not be strained, usually a 5- or 6-membered chain or ring. Retro-Claisen condensation is the reverse of the title reaction, i.e., the base-induced cleavage of 2-ketoesters
The glyoxylate cycle is a variant of the citric acid cycle. [4] It is an anabolic pathway occurring in plants and bacteria utilizing the enzymes isocitrate lyase and malate synthase. Some intermediate steps of the cycle are slightly different from the citric acid cycle; nevertheless oxaloacetate has the same function in both processes. [1]
Malate, in the mitochondrial matrix, can be used to make pyruvate (catalyzed by malic enzyme) or oxaloacetic acid, both of which can enter the citric acid cycle. Glutamine can also be used to produce oxaloacetate during anaplerotic reactions in various cell types through "glutaminolysis", which is also seen in many c-Myc transformed cells. [3]
They generally form by the Claisen condensation. The presence of the keto group at the beta position allows them to easily undergo thermal decarboxylation. [7] Gamma-keto acids, Gamma-ketoacids, or 4-oxoacids have the ketone group at the third carbon from the carboxylic acid. Levulinic acid is an example.
Citrate synthase has three key amino acids in its active site (known as the catalytic triad) which catalyze the conversion of acetyl-CoA [H 3 CC(=O)−SCoA] and oxaloacetate [− O 2 CCH 2 C(=O)CO 2 −] into citrate [− O 2 CCH 2 C(OH)(CO 2 −)CH 2 CO 2 −] and H−SCoA in an aldol condensation reaction. The citrate product is said to be ...
The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle (tricarboxylic acid cycle) [1] [2] —is a series of biochemical reactions to release the energy stored in nutrients through the oxidation of acetyl-CoA derived from carbohydrates, fats, proteins, and alcohol.
The Krebs cycle, also known as the TCA cycle or Citric Acid cycle, is a biochemical pathway that facilitates the breakdown of glucose in a cell. Both citrate and malate involved in the citrate-malate shuttle are necessary intermediates of the Krebs cycle. [9]