Phosphoenolpyruvate carboxylase (also known as PEP carboxylase, PEPCase, or PEPC; EC 4.1.1.31, PDB ID: 3ZGE) is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO3−) to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate and inorganic phosphate:[1]