Oxaloacetic acid is a dicarboxylic acid. It is an intermediate in the citric acid cycle. It is highly soluble in water and is present ubiquitously. It is produced in the mitochondria by the action of pyruvate carboxylase on pyruvate. Breakdown products of oxaloacetate includes malate, pyruvate and aspartic acid.

Oxaloacetic acid has been used as a substrate for measuring citrate synthase activity in cybrids and neuroblastoma cells. It has also been used for measuring malate dehydrogenase reactivation.

Oxaloacetic acid being an intermediate in the tri carboxylic cycle is central to metabolism. It is part of gluconeogenesis pathway. Mutation in pyruvate carboxylase leads to decreased production of oxaloacetate. It inhibits succinate dehydrogenase and is a key regulator of mitochondrial metabolism.