Journal Title
Title of Journal: Biometals
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Publisher
Springer Netherlands
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Authors: Günther Weber Nicolaus von Wirén Heiko Hayen
Publish Date: 2008/03/06
Volume: 21, Issue: 5, Pages: 503-513
Abstract
Phytosiderophores PS are strong iron chelators produced by graminaceous plants under iron deficiency The ability of released PS to chelate ironIII and subsequent uptake of this chelate into roots by YS1type transport proteins are wellknown The mechanism of iron release from the stable chelate inside the plant cell however is unclear One possibility involves the reduction of ferric PS in the presence of an ironII chelator via ternary complex formation Here the conversion of ferric PS species by ascorbate in the presence of the intracellular ligand nicotianamine NA has been investigated at cytosolic pH pH 73 leading to the formation of a ferrous NA chelate This reaction takes place when supplying FeIII as a chelate with 2′deoxymugineic acid DMA mugineic acid MA and 3epihydroxymugineic acid epiHMA with the reaction rate decreasing in this order The progress of the conversion of ferric DMA to ferrous NA was monitored in realtime by high resolution mass spectrometry FTICRMS and the results are complemented by electrochemical measurements cyclic voltammetry which allows detecting reactive intermediates and their change with time at high sensitivity Hence the combined results of electrochemistry and mass spectrometry indicate an ascorbatemediated mechanism for the iron release from ferric PS which highlights the role of ascorbate as a simple but effective plant reductantWe thank E Scheuermann Hohenheim University Germany for supply of purified phytosiderophores Profs T Kitahara and S Mori University of Tokyo Japan for supply of synthesized NA and the Deutsche Forschungsgemeinschaft for financial support to GW grants WE 2422/5 and to NvW grants WI 1728/6 Financial support from the Ministerium für Innovation Wissenschaft Forschung und Technologie des Landes NordrheinWestfalen and by the Bundesministerium für Bildung und Forschung is gratefully acknowledged
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