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Oxaloacetic acid

Oxaloacetic acid
IUPAC name Oxobutanedioic acid
Other names Oxaloacetic acid
Oxalacetic acid
Oxosuccinic acid
CAS number 328-42-7
EINECS number 206-329-8
Molecular formula C4H4O5
Molar mass 132.07 g/mol
Density  ? g/cm3
Melting point

161 °C

Std enthalpy of
-943.21 kJ/mol
Std enthalpy of
-1205.58 kJ/mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Oxaloacetic acid is an organic compound with the chemical formula HO2CC(O)CH2CO2H. It also has other names (see Table) and its conjugate base is called "oxaloacetate." 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.

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). The enol proton has a pKa value of 13.02. The enzyme fumarase A from E. coli catalyses the conversion between the keto and enol forms.

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.



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