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)⁻.

[edit] 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

[edit] 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.

[edit] See also

• dioxosuccinic acid

[edit] 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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