Hydrolysis of phosphodiesters by diiron complexes: design of nonequivalent iron sites in purple acid phosphatase models.
New mu-oxo-diferric complexes have been designed for hydrolysis of phosphodiesters. To mimic the diiron active site of purple acid phosphatase, a combinatorial method has been used to select complexes containing two distinct iron coordination spheres. The introduction of a bidentate ligand, a substituted phenanthroline (L) into complex 1, [Fe2O(bipy)4(OH2)2](NO3)4, generates in solution the complex [Fe2O(bipy)3(L)(OH2)2](NO3)4 as shown by ESI/MS and 1H NMR studies. The latter complex was found to be 20-fold more active than complex 1. On the basis of kinetic studies, we demonstrated that the complex [Fe2O(bipy)3(L)(OH)(OH2)](NO3)3 was the active species and the reaction proceeded through the formation of a ternary complex in which one iron binds a hydroxide and the second, the substrate. At nonsaturating concentrations of the substrate, the increased activity with increased methyl substituents in L was due to an increased affinity of the complex for the substrate. The activity of [Fe2O(bipy)3(33'44'Me2-Phen)(OH2)2](NO3)4 [33'44'Me2Phen = 3,3',4,4'-dimethyl-1,10-phenanthroline] was found to be comparable to that reported for Co(III) or Ce(IV) complexes.
Verge
François
F
Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, Université Joseph Fourier/DRDC/CEA, UMR CNRS 5047, Grenoble, 17 rue des Martyrs, 38054 Grenoble, France.
Lebrun
Colette
C
Fontecave
Marc
M
Ménage
Stéphane
S
D000135:Acid Phosphatase / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D006023:Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010755:Organophosphates / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry
D006023:Glycoproteins; D008024:Ligands; D010755:Organophosphates; D014867:Water; D007501:Iron; C091137:purple acid phosphatase; D000135:Acid Phosphatase