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Title: Cyanide binding to human plasma heme-hemopexin: A comparative study

Abstract

Highlights: Black-Right-Pointing-Pointer Cyanide binding to ferric HHPX-heme-Fe. Black-Right-Pointing-Pointer Cyanide binding to ferrous HHPX-heme-Fe. Black-Right-Pointing-Pointer Dithionite-mediated reduction of ferric HHPX-heme-Fe-cyanide. Black-Right-Pointing-Pointer Cyanide binding to HHPX-heme-Fe is limited by ligand deprotonation. Black-Right-Pointing-Pointer Cyanide dissociation from HHPX-heme-Fe-cyanide is limited by ligand protonation. -- Abstract: Hemopexin (HPX) displays a pivotal role in heme scavenging and delivery to the liver. In turn, heme-Fe-hemopexin (HPX-heme-Fe) displays heme-based spectroscopic and reactivity properties. Here, kinetics and thermodynamics of cyanide binding to ferric and ferrous hexa-coordinate human plasma HPX-heme-Fe (HHPX-heme-Fe(III) and HHPX-heme-Fe(II), respectively), and for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex, at pH 7.4 and 20.0 Degree-Sign C, are reported. Values of thermodynamic and kinetic parameters for cyanide binding to HHPX-heme-Fe(III) and HHPX-heme-Fe(II) are K = (4.1 {+-} 0.4) Multiplication-Sign 10{sup -6} M, k{sub on} = (6.9 {+-} 0.5) Multiplication-Sign 10{sup 1} M{sup -1} s{sup -1}, and k{sub off} = 2.8 Multiplication-Sign 10{sup -4} s{sup -1}; and H = (6 {+-} 1) Multiplication-Sign 10{sup -1} M, h{sub on} = 1.2 Multiplication-Sign 10{sup -1} M{sup -1} s{sup -1}, and h{sub off} = (7.1 {+-} 0.8) Multiplication-Sign 10{sup -2} s{sup -1}, respectively. The value of the rate constant for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex is l = 8.9more » {+-} 0.8 M{sup -1/2} s{sup -1}. HHPX-heme-Fe reactivity is modulated by proton acceptor/donor amino acid residue(s) (e.g., His236) assisting the deprotonation and protonation of the incoming and outgoing ligand, respectively.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Laboratorio Interdipartimentale di Microscopia Elettronica, Universita Roma Tre, Roma (Italy)
  2. (Italy)
  3. Istituto Nazionale di Biostrutture e Biosistemi, Roma (Italy)
  4. Dipartimento di Biologia, Universita Roma Tre, Roma (Italy)
Publication Date:
OSTI Identifier:
22210331
Resource Type:
Journal Article
Journal Name:
Biochemical and Biophysical Research Communications
Additional Journal Information:
Journal Volume: 428; Journal Issue: 2; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0006-291X
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ALBUMINS; AMINO ACIDS; CHLAMYDOMONAS; CYANIDES; HEME; HEMOGLOBIN; LIGANDS; LIPOPROTEINS; LIVER; MYCOBACTERIUM TUBERCULOSIS; MYOGLOBIN; PH VALUE; REACTIVITY; SCAVENGING; THERMODYNAMICS

Citation Formats

Ascenzi, Paolo, E-mail: ascenzi@uniroma3.it, Istituto Nazionale di Biostrutture e Biosistemi, Roma, Leboffe, Loris, and Polticelli, Fabio. Cyanide binding to human plasma heme-hemopexin: A comparative study. United States: N. p., 2012. Web. doi:10.1016/J.BBRC.2012.10.027.
Ascenzi, Paolo, E-mail: ascenzi@uniroma3.it, Istituto Nazionale di Biostrutture e Biosistemi, Roma, Leboffe, Loris, & Polticelli, Fabio. Cyanide binding to human plasma heme-hemopexin: A comparative study. United States. doi:10.1016/J.BBRC.2012.10.027.
Ascenzi, Paolo, E-mail: ascenzi@uniroma3.it, Istituto Nazionale di Biostrutture e Biosistemi, Roma, Leboffe, Loris, and Polticelli, Fabio. Fri . "Cyanide binding to human plasma heme-hemopexin: A comparative study". United States. doi:10.1016/J.BBRC.2012.10.027.
@article{osti_22210331,
title = {Cyanide binding to human plasma heme-hemopexin: A comparative study},
author = {Ascenzi, Paolo, E-mail: ascenzi@uniroma3.it and Istituto Nazionale di Biostrutture e Biosistemi, Roma and Leboffe, Loris and Polticelli, Fabio},
abstractNote = {Highlights: Black-Right-Pointing-Pointer Cyanide binding to ferric HHPX-heme-Fe. Black-Right-Pointing-Pointer Cyanide binding to ferrous HHPX-heme-Fe. Black-Right-Pointing-Pointer Dithionite-mediated reduction of ferric HHPX-heme-Fe-cyanide. Black-Right-Pointing-Pointer Cyanide binding to HHPX-heme-Fe is limited by ligand deprotonation. Black-Right-Pointing-Pointer Cyanide dissociation from HHPX-heme-Fe-cyanide is limited by ligand protonation. -- Abstract: Hemopexin (HPX) displays a pivotal role in heme scavenging and delivery to the liver. In turn, heme-Fe-hemopexin (HPX-heme-Fe) displays heme-based spectroscopic and reactivity properties. Here, kinetics and thermodynamics of cyanide binding to ferric and ferrous hexa-coordinate human plasma HPX-heme-Fe (HHPX-heme-Fe(III) and HHPX-heme-Fe(II), respectively), and for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex, at pH 7.4 and 20.0 Degree-Sign C, are reported. Values of thermodynamic and kinetic parameters for cyanide binding to HHPX-heme-Fe(III) and HHPX-heme-Fe(II) are K = (4.1 {+-} 0.4) Multiplication-Sign 10{sup -6} M, k{sub on} = (6.9 {+-} 0.5) Multiplication-Sign 10{sup 1} M{sup -1} s{sup -1}, and k{sub off} = 2.8 Multiplication-Sign 10{sup -4} s{sup -1}; and H = (6 {+-} 1) Multiplication-Sign 10{sup -1} M, h{sub on} = 1.2 Multiplication-Sign 10{sup -1} M{sup -1} s{sup -1}, and h{sub off} = (7.1 {+-} 0.8) Multiplication-Sign 10{sup -2} s{sup -1}, respectively. The value of the rate constant for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex is l = 8.9 {+-} 0.8 M{sup -1/2} s{sup -1}. HHPX-heme-Fe reactivity is modulated by proton acceptor/donor amino acid residue(s) (e.g., His236) assisting the deprotonation and protonation of the incoming and outgoing ligand, respectively.},
doi = {10.1016/J.BBRC.2012.10.027},
journal = {Biochemical and Biophysical Research Communications},
issn = {0006-291X},
number = 2,
volume = 428,
place = {United States},
year = {2012},
month = {11}
}