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Title: Structure-function mimicry of oxidized purple acid phosphatase-PAP<sub>ox</sub> – A new functional model
Authors: Waghmode, Shobha A
Date, Sadgopal K
Gupta, Vidya S
Rane, Sandhya Y
Keywords: Bioinorganic chemistry
Nuclease activity
PAPox analogues
DNA cleavage
Antiferromagnetic exchange
Issue Date: Aug-2010
Publisher: CSIR
Series/Report no.: Int. Cl.<sup>9</sup> C07F15/02
Abstract: Electronic structure and spectroscopic properties of the novel diiron active site of oxidized mammalian purple acid phosphatase analogues, Fe-6: [Fe<sub>2</sub> (<img src='/image/spc_char/micro.gif' border=0> -O) (<img src='/image/spc_char/micro.gif' border=0> -OAc) (4HNSQ<sub>ox</sub>)<sup>∸</sup>(ONSQ<sub>ox</sub>)<sup>2</sup><sup>∸</sup>(H<sub>2</sub>O)<sub>4</sub>] and Fe-7: [Fe<sub>2</sub> (<img src='/image/spc_char/micro.gif' border=0> -O) (<img src='/image/spc_char/micro.gif' border=0> -OAc)(ONSQ<sub>ox</sub>)<sup>2</sup><b><sup>∸</sup></b>(OAc) (H<sub>2</sub>O)<sub>4</sub>] are described. Magnetic susceptibility SQUID data of Fe-6 are best fitted to Heisenberg’s isotropic spin pair (<i style="">S</i> = 5/2, 3/2) model using magnetic parameters <i>g</i> = 2 and <i style="">J</i> = – 36.8 cm<sup>-1</sup> with <i>R</i> factor = 6.4 × 10<sup>-4</sup>.<sup> </sup>The antiferromagnetic exchange establishes Fe(III)-O-Fe(III) dimeric core with Fe(III) site having two radical ligations in the naphthosemiquinone oxime form of lawsone oxime. In the model compound Fe-7 of oxidized purple acid phosphatase, bridged and terminal acetate functions are identified according to their different energies of activations, i.e, ~34 and 58 kJ mol<sup>-1</sup> respectively. Also, the reduced naphthoquinone oxime form of ligand is characterized by its energy of activation (~15 kJ mol<sup>-1</sup>) from pyrolytic reaction. Mössbauer parameters, <img src='/image/spc_char/delta1.gif' border=0> = 0.4 mm s<sup>-1</sup> and D<i>E</i><sub>Q</sub> = 0.8 mm s<sup>-1</sup>, are characteristics of oxidized Fe(III) in high spin octahedral site. Only Fe-6 shows analogous physiological DNA cleavage activity on pUC19 plasmid and acts as a good model of oxidized purple acid phosphatase enzyme.
Description: 1023-1029
Appears in Collections:IJC-A Vol.49A(08) [August 2010]

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