IRON REDUCTASE SYSTEMS ON THE PLANT PLASMA-MEMBRANE - A REVIEW

Higher plant roots, leaf mesophyll tissue, protoplasts as well as gree n algae are able to reduce extra-cellular ferricyanide and ferric chel ates. In roots of dicotyledonous and nongraminaceous, monocotyledonous plants, the rate of ferric reduction is increased by iron deficiency. This reduction is an obligatory prerequisite for iron uptake and is m ediated by redox systems localized on the plasma membrane. Plasma memb rane-bound iron reductase systems catalyze the transmembrane electron transport from cytosolic reduced pyridine nucleotides to extracellular iron compounds. Natural and synthetic ferric complexes can act as ele ctron acceptors. This paper gives an overview about the present knowle dge on iron reductase systems at the plant plasma membrane with specia l emphasis on biochemical characteristics and localisation.