title: The binding of aluminum to mugineic acid and related compounds as studied by potentiometric titration.
abstract: The phytosiderophores, mugineic acid (MA) and epi-hydroxymugineic acid (HMA), together with a related compound, nicotianamine (NA), were investigated for their ability to bind Al(III). Potentiometric titration analysis demonstrated that MA and HMA bind Al(III), in contrast to NA which does not under normal physiological conditions. With MA and HMA, in addition to the Al complex (AlL), the protonated (AlLH) and deprotonated (AlLH(-1)) complexes were identified from an analysis of titration curves, where L denotes the phytosiderophore form in which all the carboxylate functions are ionized. The equilibrium formation constants of the Al(III) phytosiderophore complexes are much smaller than those of the corresponding Fe(III) complexes. The higher selectivity of phytosiderophores for Fe(III) over Al(III) facilitates Fe(III) acquisition in alkaline conditions where free Al(III) levels are higher than free Fe(III) levels.
authors.affiliation: Department of Applied Biological Chemistry, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. ayoshim@mail.ecc.u-tokyo.ac.jp
authors.forename: Etsuro
authors.initials: E
authors.lastname: Yoshimura
authors.forename: Hicham
authors.initials: H
authors.lastname: Kohdr
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mori
authors.forename: Robert C
authors.initials: RC
authors.lastname: Hider
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D001383:Azetidinecarboxylic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D011199:Potentiometry; D013237:Stereoisomerism; D017186:Titrimetry
chemical_list: C082893:nicotianamine; D001383:Azetidinecarboxylic Acid; C052865:3-hydroxymugineic acid; D000535:Aluminum; C052863:mugineic acid