Involved in the gluconeogenesis, in growth on fatty acids and is important for initiation of infection in the macrophages. Catalyzes the GTP-dependent 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. It can also use IDP or ADP, but with a lower activity. GTP + oxaloacetate = CO2 + GDP + phosphoenolpyruvate Binds 1 Mn(2+) ion per subunit. Can also use Co(2+) ion. Inhibited by oxalate and by alpha-ketoglutarate. In vitro, the enzyme is stimulated by reducing agents such as dithiothreitol (DTT), reduced glutathione and 2-mercaptoethanol. Optimum pH is between 7 and 7.4. Optimum temperature is 70 degrees Celsius. Carbohydrate biosynthesis; gluconeogenesis. Monomer. Cells lacking this gene are inhibited when they grow on acetate and palmitate. Belongs to the phosphoenolpyruvate carboxykinase [GTP] family.