Forms oxaloacetate, a four-carbon dicarboxylic acid source for the tricarboxylic acid cycle. oxaloacetate + phosphate = hydrogencarbonate + phosphoenolpyruvate The enzyme has distinct binding sites for each of the allosteric effectors such as acetyl-CoA, fructose 1,6-bisphosphate, guanosine 3'-diphosphate 5'-diphosphate, long chain fatty acids, and L-aspartate. Homotetramer. Belongs to the PEPCase type 1 family.