oxaloacetic acid

Oxaloacetic acid
IUPAC name	Oxobutanedioic acid
Other names	Oxaloacetic acid Oxalacetic acid Oxosuccinic acid
Identifiers
CAS number	328-42-7 Y
EC number	206-329-8
SMILES	OC(C(CC(O)=O)=O)=O
ChemSpider ID	945
Properties
Molecular formula	C4H4O5
Molar mass	132.07 g/mol
Density	? g/cm3
Melting point	161 °C
Thermochemistry
Std enthalpy of formation ΔfHo298	-943.21 kJ/mol
Std enthalpy of combustion ΔcHo298	-1205.58 kJ/mol
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Oxaloacetic 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)⁻.

Function

This four-carbon dicarboxylic acid is a protonated variant of oxaloacetate, which is an intermediate of the citric acid cycle^[1] 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.

Relationship of oxaloacetic acid, malic acid, and aspartic acid

Chemical properties

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 pK_a 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.

See also

• dioxosuccinic acid

References

v • d • e 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

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