Reactivity of M-II metal-substituted derivatives of pig purple acid phosphatase (Uteroferrin) with phosphate

Twitchett, M. B., Schenk, G., Aquino, M. A. S., Yiu, D. T. Y., Lau, T. C. and Sykes, A. G. (2002) Reactivity of M-II metal-substituted derivatives of pig purple acid phosphatase (Uteroferrin) with phosphate. Inorganic Chemistry, 41 22: 5787-5794. doi:10.1021/ic020037f


Author Twitchett, M. B.
Schenk, G.
Aquino, M. A. S.
Yiu, D. T. Y.
Lau, T. C.
Sykes, A. G.
Title Reactivity of M-II metal-substituted derivatives of pig purple acid phosphatase (Uteroferrin) with phosphate
Journal name Inorganic Chemistry   Check publisher's open access policy
ISSN 0020-1669
Publication date 2002-01-01
Year available 2002
Sub-type Article (original research)
DOI 10.1021/ic020037f
Open Access Status Not yet assessed
Volume 41
Issue 22
Start page 5787
End page 5794
Total pages 8
Place of publication Washington
Publisher Amer Chemical Soc
Language eng
Abstract The Fell of the binuclear (FeFeIII)-Fe-II active site of pig purple acid phosphatase (uteroferrin) has been replaced in turn by five M-II ions (Mn-II, Co-II, Ni-II, Cu-II, and Zn-II). An uptake of 1 equiv of M-II is observed in all cases except that of Cu-II, when a second more loosely bound Cu-II is removed by treatment with edta. The products have been characterized by different analytical procedures and by UV-vis spectrophotometry. At 25degreesC, 1 = 0.100 M (NaCl), the nonenzymatic reactions with H2PO4- give the mu-phosphato product, and formation constants K/M-1 show an 8-fold spread at pH 4.9 of 740 (Mn), 165 (Fe), 190 (Co), 90 (Ni), 800 (Cu), 380 (Zn). The variations in K correlate well with stability constants for the complexing of H2PO4- and (CH3O)HPO3- with M-II hexaaqua ions. At pH 4.9 with [H2PO4-] greater than or equal to 3.5 mM rate constants k(obs) decrease, and an inhibition process in which a second [H2PO4-] coordinates to the dinuclear center is proposed. The mechanism considered accounts for most but not all of the features displayed. Thus K, values for the coordination of phosphate to M-II are in the range 10-60 M-1, whereas K-2 values for the bridging of the phosphate to Fe-III are in the narrower range 7.8-12.4. From the fits described K similar to 103 M-1 for the inhibition step, which is independent of the identity of M-II. Values of kobs decrease with increasing pH, giving pK(a) values which are close to 3.8 and independent of M-II (Fe-II, Zn-II, Mn-II). The acid dissociation process is assigned to Fe-III-OH2 to Fe-III-OH-, where OH- is less readily displaced by phosphate.
Keyword Chemistry, Inorganic & Nuclear
Iron Active-site
Bovine Spleen
Crystal-structure
Allantoic Fluid
Ion Complexes
Sweet-potato
Fe-mn
Mechanism
Zn
Exchange
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Chemistry and Molecular Biosciences
 
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Created: Thu, 20 Sep 2007, 01:45:26 EST