Through the carboxylation of phosphoenolpyruvate (PEP) it forms oxaloacetate, a four-carbon dicarboxylic acid source for the tricarboxylic acid cycle. oxaloacetate + phosphate = hydrogencarbonate + phosphoenolpyruvate Homotetramer. By salt stress. This isozyme is from salt-induced (CAM) plants. Belongs to the PEPCase type 1 family.