Iron assimilation in plants: reduction of a ferriphytosiderophore by NADH:nitrate reductase from squash.
NADH:nitrate reductase (EC 1.6.6.1) from squash (Cucurbita maxima Duch., cv. Buttercup) can catalyze the reduction of a ferriphytosiderophore from barley (Hordeum vulgare L. cv. Europa). Maximal activity occurs at pH 6, with an apparentK m andV max of 76 μM and 21 nmol·min(-1)·(mg protein)(-1), respectively. The ferriphytosiderophore strongly inhibits nitrate reduction catalyzed by nitrate reductase at the optimal pH for nitrate reduction, i.e. 7.5. On the contrary, nitrate is a poor inhibitor of ferriphytosiderophore reduction catalyzed by nitrate reductase at the optimal pH for this reaction, pH 6.0. Thus, squash has the potential to assimilate the iron from a ferriphytosiderophore synthesized by another plant.
Department of Biology, Loyola University of Chicago, 6525 North Sheridan Road, 60626, Chicago, IL, USA.
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Smarrelli
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Castignetti