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- Title
A Heterodinuclear Fe<sup>III</sup>Zn<sup>II</sup> Complex as a Mimic for Purple Acid Phosphatase with Site-Specific Zn<sup>II</sup> Binding.
- Authors
Roberts, Asha E.; Schenk, Gerhard; Gahan, Lawrence R.
- Abstract
Purple acid phosphatases (PAPs) are the only dinuclear metallohydrolases for which the necessity for a heterovalent active site (FeIII-MII; M = Fe, Zn or Mn) for catalysis has been established. A major goal for the synthesis of PAP biomimetics is to design a ligand in which the two coordination sites exhibit discrimination between the trivalent and divalent metal ions. With this goal in mind the ligand 2-{[bis(2-methoxyethyl)amino]methyl}-6-{[(2-hydroxybenzyl)(2-pyridylmethyl)amino]methyl}-4-methylphenol (BMMHPH2), with two distinct coordination sites, N2O2 (α) and NO3 (β), has been prepared. Although not exactly mimicking the active site of PAP, the ligand facilitated the formation of the complex [FeIIIZnII(BMMHP)(CH3COO)2](BPh4), which exhibited regioselectivity in the two metal binding sites. The phosphoesterase-like activity of the complex in 50:50 acetonitrile/water was investigated by using the substrate bis(2,4-dinitrophenyl) phosphate (BDNPP) yielding kinetically relevant p Ka values of 6.89, 7.37 and 9.00, a KM of 10.8 ± 2.1 m M and a kcat of 3.20 ± 0.38 × 10-3 s-1 (at pH = 7.5). Attempts to prepare a diiron analogue resulted in a centrosymmetric dimer, [FeIII2(BMMHPH)2(μ-OH)2](BPh4)2, with one six-coordinate FeIII atom in each of the α-sites, connected by two μ-hydroxido groups. In this Fe(μ-OH)2Fe diamond core the FeIII ions are weakly antiferromagnetically coupled, with J = -1.76 ± 0.03 cm-1. The β-sites were vacant. Attempts to replace the ZnII ion with MgII resulted in the formation of a centrosymmetric trimer, i.e. [FeIII2MgII(BMMHPH)2(CH3COO)2(CH3O)2](BPh4)2.
- Subjects
BIOINORGANIC chemistry; BIOMIMETIC synthesis; PURPLE acid phosphatases; PHOSPHODIESTERS; BINDING sites
- Publication
European Journal of Inorganic Chemistry, 2015, Vol 2015, Issue 19, p3076
- ISSN
1434-1948
- Publication type
Article
- DOI
10.1002/ejic.201500351