A SUCCINATE-OXIDIZING NITRATE REDUCTASE IS LOCATED AT THE PLASMA-MEMBRANE OF PLANT-ROOTS

Plasma-membrane-bound nitrate reductase (PM-NR) is located in roots an d leaves of tobacco (Nicatiana tabacum L. cv. Samsun) and reduces nitr ate with NADH as electron donor. When plasma membranes were prepared u nder specific protecting conditions, a PM-NR of roots was detected tha t accepts electrons from succinate to reduce nitrate. Comparison betwe en the succinate dehydrogenase of mitochondria and the succinate-oxidi sing PM-NR of roots indicated that they are two different enzymes. Par tial purification of the nitrate reductase forms by anion-exchange chr omatography indicated that succinate and NADH supply electrons to the same plasma-membrane-bound protein.