Oxaloacetic acid, also known as ‘oxalacetic acid’, is an α-keto acid and a key component of cellular metabolism in its conjugate base form, oxaloacetate. This is an oxodicarboxylic acid that has a single oxo group of succinic acid, with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid is a metabolic intermediate in many processes that occur in animals in the form of its conjugate base oxaloacetate.
As a metabolite, oxaloacetic acid is an oxo dicarboxylic acid and a C4-dicarboxylic acid. It is involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, the synthesis of fatty acids and the cycle of citric acids. Oxaloacetate reacts in the first step of the citric acid cycle with acetyl coenzyme A and water to form citrate, which is regenerated in the final step by oxidation of L-malate.
Oxaloacetic acid undergoes successive deprotonations to give the dianion:
HO2CC(O)CH2CO2H ⇌ −O2CC(O)CH2CO2H + H+ pKa = 2.22
−O2CC(O)CH2CO2H ⇌ −O2CC(O)CH2CO2− + H+, pKa = 3.89
Oxaloacetic acid is an intermediate in gluconeogenesis produced by carboxylation of pyruvate in mitochondria and subsequently decarboxylated and phosphorylated to form phosphoenolpyruvate. Oxaloacetate forms in several ways in nature; it may arise from transmission or de-amination of amino acid. It’s also involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, aminoalkanoic acid synthesis, and carboxylic acid synthesis.
Oxaloacetate may be converted to aspartate through the addition of glutamate to an amino group. Oxaloacetate is then decarboxylated and phosphorylated by carboxykinase phosphoenolpyruvate and becomes 2-phosphoenolpyruvate using triphosphate guanosine (GTP) as the source of phosphate. Upon more downstream processing Glucose is collected.
A dicarboxylic acid ketone that’s a vital metabolic intermediate of the acid cycle; nevertheless oxaloacetate has an identical function in both processes. This suggests that oxaloacetate during this cycle also acts because of the primary reactant and final product. Six essential amino acids and three nonessential are synthesized from oxaloacetate and pyruvate.
Oxaloacetate (30 μmol/min per 100 g for a half-hour, i.v.) reduces blood glutamate levels, the severity of neurological dysfunction, and brain edema in a very rat model of closed head injury. Asparagine, methionine, lysine, and threonine are synthesized by aspartate; therefore, given the importance of oxaloacetate as without it, no aspartate would be formed, nor would the following other amino acids be produced either.