- Oxaloacetic acid
Oxaloacetic acid Identifiers CAS number PubChem ChemSpider EC number ChEBI Jmol-3D images Image 1 Properties Molecular formula C4H4O5 Molar mass 132.07 g/mol Density ? g/cm3 Melting point
Thermochemistry Std enthalpy of
o298 -943.21 kJ/mol Std enthalpy of
o298 -1205.58 kJ/mol (what is: /?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Oxaloacetic acid (also oxalacetic acid) is an organic compound with the chemical formula C4H4O5 or HOOC-(C=O)-(CH2)-COOH. It also has other names (see the table).
Its fully deprotonated derivative is the oxaloacetate anion, C4H2O52− or [(C=O)2(CH2)(C=O)]2−; this name is also used for esters that contain the divalent [-O(C=O)2(CH2)(C=O)O-] moiety. Loss of a single proton gives the acid's conjugate base, the anion hydrogenoxaloacetate anion H(C=O)2(CH2)(C=O)−.
This four-carbon dicarboxylic acid is a protonated variant of oxaloacetate, which is an intermediate of the citric acid cycle and gluconeogenesis. Oxaloacetate forms upon oxidation of L-malate, catalysed by malate dehydrogenase, and reacts with Acetyl-CoA to form citrate, catalysed by citrate synthase. It also forms in the mesophyll of plants by the condensation of CO2 with phosphoenolpyruvate, catalysed by PEP Carboxykinase. It can arise from pyruvate via an anaplerotic reaction. Oxaloacetate is also a potent inhibitor of Complex II.
The enol forms of oxaloacetic acid are particularly stable, so much so that the two isomers have different melting points (152 °C cis, 184 °C trans).[clarification needed] The enol proton has a pKa value of 13.02.
Oxaloacetate is unstable in solution, decomposing to pyruvate by decarboxylation over a period of hours (room temperature) or days (0 °C). Refrigerated storage of the solid is therefore recommended.
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.
- ^ "Citric Acid Cycle Reactions". http://www.elmhurst.edu/~chm/vchembook/611citricrx.html. Retrieved 2009-04-18.
- ^ The interactive pathway map can be edited at WikiPathways: "TCACycle_WP78". http://www.wikipathways.org/index.php/Pathway:WP78.
Citric Acid Cycle Metabolic Pathway Oxaloacetate Malate Fumarate Succinate Succinyl-CoA Acetyl-CoA NADH + H+ NAD+ H2O FADH2 FAD CoA + ATP(GTP) Pi + ADP(GDP) + H2O NADH + H+ + CO2 CoA NAD+ H2O H2O NAD(P)+ NAD(P)H + H+ CO2 Citrate cis-Aconitate Isocitrate Oxalosuccinate α-Ketoglutarate K→acetyl-CoA GG→pyruvate→citrateG→glutamate→
α-ketoglutarateotherG→fumarateG→oxaloacetatesee urea cycle
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