The citric acid cycle (CAC)—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.
Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processes that occur in animals. It takes part in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle.
Malate dehydrogenase (EC 1.1.1.37) (MDH) is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD+ to NADH. This reaction is part of many metabolic pathways, including the citric acid cycle. Other malate dehydrogenases, which have other EC numbers and catalyze other reactions oxidizing malate, have qualified names like malate dehydrogenase (NADP+).
The malate-aspartate shuttle is a biochemical system for translocating electrons produced during glycolysis across the semipermeable inner membrane of the mitochondrion for oxidative phosphorylation in eukaryotes. These electrons enter the electron transport chain of the mitochondria via reduction equivalents to generate ATP. The shuttle system is required because the mitochondrial inner membrane is impermeable to NADH, the primary reducing equivalent of the electron transport chain. To circumvent this, malate carries the reducing equivalents across the membrane.
In enzymology, a D-malate dehydrogenase (decarboxylating) (EC 1.1.1.83) is an enzyme that catalyzes the chemical reaction
Malate dehydrogenase (decarboxylating) (EC 1.1.1.39) or NAD-malic enzyme (NAD-ME) is an enzyme that catalyzes the chemical reaction
In enzymology, a malate dehydrogenase (NADP+) (EC 1.1.1.82) is an enzyme that catalyzes the chemical reaction
In enzymology, a malate dehydrogenase (oxaloacetate-decarboxylating) (EC 1.1.1.38) is an enzyme that catalyzes the chemical reaction below
Malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1.1.1.40) or NADP-malic enzyme (NADP-ME) is an enzyme that catalyzes the chemical reaction in the presence of a bivalent metal ion:
In enzymology, a sterol-4alpha-carboxylate 3-dehydrogenase (decarboxylating) (EC 1.1.1.170) is an enzyme that catalyzes the chemical reaction
In enzymology, an arogenate dehydrogenase [NAD(P)+] (EC 1.3.1.79) is an enzyme that catalyzes the chemical reaction
In enzymology, a malate dehydrogenase (quinone) (EC 1.1.5.4), formerly malate dehydrogenase (acceptor) (EC 1.1.99.16), is an enzyme that catalyzes the chemical reaction
In enzymology, a malate oxidase (EC 1.1.3.3) is an enzyme that catalyzes the chemical reaction
Aspartate dehydrogenase (EC 1.4.1.21) is an enzyme that catalyzes the chemical reaction
In enzymology, a glycine dehydrogenase (EC 1.4.1.10) is an enzyme that catalyzes the chemical reaction
Malate dehydrogenase, mitochondrial also known as malate dehydrogenase 2 is an enzyme that in humans is encoded by the MDH2 gene.
In molecular biology, the isocitrate/isopropylmalate dehydrogenase family is a protein family consisting of the evolutionary related enzymes isocitrate dehydrogenase, 3-isopropylmalate dehydrogenase and tartrate dehydrogenase.
Malate dehydrogenase is an enzyme that reversibly catalyzes the oxidation of malate to oxaloacetate using the reduction of NAD+ to NADH.
Malate dehydrogenase (NAD(P)+) (EC 1.1.1.299, MdH II, NAD(P)+-dependent malate dehyrogenase) is an enzyme with systematic name (S)-malate:NAD(P)+ oxidoreductase. This enzyme catalyses the following chemical reaction
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