In sugarcane plant, 14CO2 is fixed in malic acid, the enzyme that fixes CO2 in this reaction is
Phosphoenol pyruvate is formed from the decarboxylation of oxloacetate and hydrolysis of one guanosine triphosphate molecule. This reaction is catalyzed by the enzyme phosphoenolpyruvate carboxylase. This reaction is a rate limiting step in gluconeogenesis.
GTP + Oxaloacetate -----> GDP + Phosphoenolpyruvate + CO2.