title: An adenine nucleotide-phosphoenolpyruvate counter-transport system in C3 and C4 plant chloroplasts.
abstract: A rapid counter-exchange between ATP and phosphoenolpyruvate (PEP) has been demonstrated in pea and maize mesophyll chloroplasts. Chloroplasts preloaded with either [14C] ATP or [14C] PEP readily exchange the radioactive compound with the externally added anions, ATP or PEP, whereas, cold external Pi counter-transports only with internal [14C] PEP. Flooding the system with cold Pi, however, will significantly reduce the counter-transport of external cold PEP with internal [14C] ATP. This ATP-PEP exchange is also markedly decreased by lowering the incubation temperature. The results indicate that the ATP-PEP counter-exchange could represent a key transport system in plant chloroplasts and may be particularly important in the photosynthesis of C4 plants. Furthermore, they provide information required to elucidate the mechanism of the ATP-PEP counter-transport system.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001693:Biological Transport, Active; D002250:Carbon Radioisotopes; D002736:Chloroplasts / Q000378:metabolism*; D007700:Kinetics; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D013696:Temperature; D003313:Zea mays / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D010710:Phosphates; D010728:Phosphoenolpyruvate; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D009713:Nucleotidyltransferases