Phosphate ester cleavage promoted by a tetrameric iron(III) complex

Kantacha, A, Buchholz, R, Smith, SJ, Schenk, G and Gahan, LR (2011) Phosphate ester cleavage promoted by a tetrameric iron(III) complex. Journal of Biological Inorganic Chemistry, 16 1: 25-32. doi:10.1007/s00775-010-0696-0

Author Kantacha, A
Buchholz, R
Smith, SJ
Schenk, G
Gahan, LR
Title Phosphate ester cleavage promoted by a tetrameric iron(III) complex
Journal name Journal of Biological Inorganic Chemistry   Check publisher's open access policy
ISSN 0949-8257
Publication date 2011-01
Year available 2010
Sub-type Article (original research)
DOI 10.1007/s00775-010-0696-0
Volume 16
Issue 1
Start page 25
End page 32
Total pages 8
Place of publication Heidelberg, Germany
Publisher Springer
Collection year 2011
Language eng
Formatted abstract
The purple acid phosphatases (PAPs) are the only binuclear metallohydrolases where the necessity for a heterovalent active site [Fe(III)–M(II) (M is Fe, Zn or Mn)] for catalysis has been established. The paradigm for the construction of PAP biomimetics, both structural and functional, is that the ligands possess characteristics which mimic those of the donor sites of the metalloenzyme and permit discrimination between trivalent and divalent metal ions. The donor atom set of the ligand 2-((2-hydroxy-5-methyl-3-((pyridin-2-ylmethylamino)methyl)benzyl)(2-hydroxybenzyl)amino)acetic acid (H3HPBA) mimics that of the active site of PAP although the iron(III) complex of this ligand has been characterized as the tetramer [Fe4(HPBA)2(μ-CH3COO)2(μ-O)(μ-OH)(OH2)2]ClO4·5H2O. The phosphoesterase-like activity of the complex in 1:1 acetonitrile/water has now been investigated using the substrate 2,4-bis(dinitrophenyl)phosphate. The pH dependence of the catalytic rate revealed a non-symmetric bell-shaped profile, with a finite but non-zero rate at high pH. Unlike the traditional approach usually employed to analyse these bell-shaped profiles, the approach used here involved incorporating additional species which contribute to the overall activity. Employing this approach, we show that the complex has a kcat of 1.6 (±0.2) × 10−3 s−1, three kinetically relevant pKa values of 5.3, 6.2 and 8.4, with KM of 7.4 ± 0.6 mM. The kinetic parameters are similar to those reported for heterovalent PAP biomimetics. Additionally, it is observed that, unlike the enzyme, the oxidation state is not the determining factor for catalytic activity.
© SBIC 2010
Keyword Purple acid phosphatase
Phosphodiester-degrading enzyme
Binuclear metallohydrolases
Iron complexes
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online: 28 August 2010

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
School of Chemistry and Molecular Biosciences
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Citation counts: TR Web of Science Citation Count  Cited 9 times in Thomson Reuters Web of Science Article | Citations
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Created: Sun, 27 Feb 2011, 00:07:15 EST