Involved in the gluconeogenesis. Catalyzes the conversion of oxaloacetate (OAA) to phosphoenolpyruvate (PEP), the rate-limiting step in the metabolic pathway that produces glucose from lactate and other precursors derived from the citric acid cycle. GTP + oxaloacetate = CO2 + GDP + phosphoenolpyruvate Binds 1 Mn(2+) ion per subunit. Carbohydrate biosynthesis; gluconeogenesis. Monomer. Cells lacking this gene lead to the absence of PEP carboxykinase activity and the inability to grow on acetate or lactate. The presence and the level of PEP carboxykinase activity has a strong influence on the biosynthesis of glutamate and a weak influence on the biosynthesis of lysine. Belongs to the phosphoenolpyruvate carboxykinase [GTP] family.