Int J Biochem Mol Biol 2011;2(4):328-339.
Original Article
Structural evidence for the order of preference of inorganic substrates in mammalian
heme peroxidases: crystal structure of the complex of lactoperoxidase with four
inorganic substrates, SCN-, I-, Br– and Cl-
Amit K Singh, Nisha Pandey, Mau Sinha, Punit Kaur, Sujata Sharma, Tej P Singh
Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India
Received October 18, 2011; accepted November 12, 2011; Epub November 20, 2011; Published December 15, 2011
Abstract: Lactoperoxidase (LPO) is a member of the family of mammalian heme peroxidases. It catalyzes the oxidation of halides and
pseudohalides in presence of hydrogen peroxide. LPO has been co-crystallized with inorganic substrates, SCN-, I-, Br- and Cl-. The structure
determination of the complex of LPO with above four substrates showed that all of them occupied distinct positions in the substrate binding
site on the distal heme side. The bound substrate ions were separated from each other by one or more water molecules. The heme iron is
coordinated to His-351 Nε2 on the proximal side while it is coordinated to conserved water molecule W-1 on the distal heme side. W-1 is
hydrogen bonded to Br- ion which is followed by Cl- ion with a hydrogen bonded water molecule W-5' between them. Next to Cl- ion is a
hydrogen bonded water molecule W-7' which in turn is hydrogen bonded to W-8' and N atom of SCN-. W-8' is hydrogen bonded to W-9' which is
hydrogen bonded to I-. SCN- ion also interacts directly with Asn-230 and through water molecules with Ser-235 and Phe-254. Therefore,
according to the locations of four substrate anions, the order of preference for binding to lactoperoxidase is observed as Br- > Cl- > SCN- > I-.
The positions of anions are further defined in terms of subsites where Br- is located in subsite 1, Cl- in subsite 2, SCN- in subsite 3 and I- in
subsite 4. (IJBMB1110003)
Keywords: Antimicrobial activity, heme, oxidation, peroxidase, crystal structure, complex, halide ions
Full Text PDF
Address all correspondence to:
Dr. Singh TP
Department of Biophysics, All India Institute of Medical Sciences,
Ansari Nagar, New Delhi – 110 029, India.
Tel: +91-11-2658-8931; Fax: +91-11-2658-8663
E-mail: tpsingh.aiims@gmail.com
Original Article
Structural evidence for the order of preference of inorganic substrates in mammalian
heme peroxidases: crystal structure of the complex of lactoperoxidase with four
inorganic substrates, SCN-, I-, Br– and Cl-
Amit K Singh, Nisha Pandey, Mau Sinha, Punit Kaur, Sujata Sharma, Tej P Singh
Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India
Received October 18, 2011; accepted November 12, 2011; Epub November 20, 2011; Published December 15, 2011
Abstract: Lactoperoxidase (LPO) is a member of the family of mammalian heme peroxidases. It catalyzes the oxidation of halides and
pseudohalides in presence of hydrogen peroxide. LPO has been co-crystallized with inorganic substrates, SCN-, I-, Br- and Cl-. The structure
determination of the complex of LPO with above four substrates showed that all of them occupied distinct positions in the substrate binding
site on the distal heme side. The bound substrate ions were separated from each other by one or more water molecules. The heme iron is
coordinated to His-351 Nε2 on the proximal side while it is coordinated to conserved water molecule W-1 on the distal heme side. W-1 is
hydrogen bonded to Br- ion which is followed by Cl- ion with a hydrogen bonded water molecule W-5' between them. Next to Cl- ion is a
hydrogen bonded water molecule W-7' which in turn is hydrogen bonded to W-8' and N atom of SCN-. W-8' is hydrogen bonded to W-9' which is
hydrogen bonded to I-. SCN- ion also interacts directly with Asn-230 and through water molecules with Ser-235 and Phe-254. Therefore,
according to the locations of four substrate anions, the order of preference for binding to lactoperoxidase is observed as Br- > Cl- > SCN- > I-.
The positions of anions are further defined in terms of subsites where Br- is located in subsite 1, Cl- in subsite 2, SCN- in subsite 3 and I- in
subsite 4. (IJBMB1110003)
Keywords: Antimicrobial activity, heme, oxidation, peroxidase, crystal structure, complex, halide ions
Full Text PDF
Address all correspondence to:
Dr. Singh TP
Department of Biophysics, All India Institute of Medical Sciences,
Ansari Nagar, New Delhi – 110 029, India.
Tel: +91-11-2658-8931; Fax: +91-11-2658-8663
E-mail: tpsingh.aiims@gmail.com
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