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 HPXheme-Fe (HHPX-heme-Fe(III) and HHPX-heme-Fe(11), respectively), and for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex, at pH 7.4 and 20.0 C, are reported. Values of thermodynamic and kinetic parameters for cyanide binding to HFIPX-heme-Fe(111) and HHPX-herneFe(II) are K= (4.1 +/- 0.4) x 10(-6) M. = (6.9 +/- 0.5) x 10(1) M-1 s(-1) and k(off) = 2.8 x 10(-4) s(-1); and H = (6 +/- 1) x 10(-1) M, h(on) = 1.2 x 10(-1) M-1 s(-1), and h(off) = (7.1 +/- 0.8) x 10(-2) s(-1), respectively. The value of the rate constant for the dithionite-mediated reduction of the HHPX-heme-Fe(II1)-cyanide complex is l = 8.9 0.8 M-1/2 s(-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.

Ascenzi, P., Leboffe, L., Polticelli, F. (2012). Cyanide binding to human plasma heme-hemopexin: a comparative study. BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 428(2), 239-244 [10.1016/j.bbrc.2012.10.027].

Cyanide binding to human plasma heme-hemopexin: a comparative study

ASCENZI, Paolo;POLTICELLI, Fabio
2012-01-01

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 HPXheme-Fe (HHPX-heme-Fe(III) and HHPX-heme-Fe(11), respectively), and for the dithionite-mediated reduction of the HHPX-heme-Fe(III)-cyanide complex, at pH 7.4 and 20.0 C, are reported. Values of thermodynamic and kinetic parameters for cyanide binding to HFIPX-heme-Fe(111) and HHPX-herneFe(II) are K= (4.1 +/- 0.4) x 10(-6) M. = (6.9 +/- 0.5) x 10(1) M-1 s(-1) and k(off) = 2.8 x 10(-4) s(-1); and H = (6 +/- 1) x 10(-1) M, h(on) = 1.2 x 10(-1) M-1 s(-1), and h(off) = (7.1 +/- 0.8) x 10(-2) s(-1), respectively. The value of the rate constant for the dithionite-mediated reduction of the HHPX-heme-Fe(II1)-cyanide complex is l = 8.9 0.8 M-1/2 s(-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.
Ascenzi, P., Leboffe, L., Polticelli, F. (2012). Cyanide binding to human plasma heme-hemopexin: a comparative study. BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 428(2), 239-244 [10.1016/j.bbrc.2012.10.027].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/278736
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