Oxaloacetic acid

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Oxaloacetic acid

IUPAC name	Oxobutanedioic acid
Other names	Oxaloacetic acid Oxalacetic acid Oxosuccinic acid
Identifiers
CAS number	328-42-7
EINECS number	206-329-8
SMILES	OC(C(CC(O)=O)=O)=O
Properties
Molecular formula	C₄H₄O₅
Molar mass	132.07 g/mol
Density	? g/cm³
Melting point	161 °C
Thermochemistry
Std enthalpy of formation Δ_fH^o₂₉₈	-943.21 kJ/mol
Std enthalpy of combustion Δ_cH^o₂₉₈	-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 pK_a value of 13.02. The enzyme fumarase A from E. coli catalyses the conversion between the keto and enol forms.

Oxaloacetic acid is unstable in solution, decomposing to pyruvic acid by decarboxylation over a period of hours (room temperature) or days (0 °C). Refrigerated storage of the solid is therefore recommended.

Relationship of oxaloacetic acid, malic acid, and aspartic acid

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Citric Acid Cycle Metabolic Pathway

Oxaloacetate