High Quality Content by WIKIPEDIA articles! 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) .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.