O2-mediated oxidation of hemopexin-heme(II)-NO

Mauro Fasano, Giovanni Antonini, Paolo Ascenzi

Research output: Contribution to journalArticle

Abstract

Hemopexin (HPX), serving as scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. Here, kinetics of HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO are reported. NO reacts reversibly with HPX-heme(II) yielding HPX-heme(II)-NO, according to the minimum reaction scheme:{A formula is presented}values of kon, koff, and K (=kon/koff) are (6.3 ± 0.3) × 103 M-1 s-1, (9.1 ± 0.4) × 10-4 s-1, and (6.9 ± 0.6) × 106 M-1, respectively, at pH 7.0 and 10.0 °C. O2 reacts with HPX-heme(II)-NO yielding HPX-heme(III) and multiscripts(NO, mml:none(), mml:none(), 3, -), by means of the ferric heme-bound peroxynitrite intermediate (HPX-heme(III)-N(O)OO), according to the minimum reaction scheme:{A formula is presented}the backward reaction rate is negligible. Values of hon and l are (2.4 ± 0.3) × 101 M-1 s-1 and (1.4 ± 0.2) × 10-3 s-1, respectively, at pH 7.0 and 10.0 °C. The decay of HPX-heme(III)-N(O)OO (i.e., l) is rate limiting. The HPX-heme(III)-N(O)OO intermediate has been characterized by optical absorption spectroscopy in the Soret region (λmax = 409 nm and ε409 = 1.51 × 105 M-1 cm-1). These results, representing the first kinetic evidence for HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO, might be predictive of transient (pseudo-enzymatic) function(s) of heme carriers.

Original languageEnglish
Pages (from-to)704-712
Number of pages9
JournalBiochemical and Biophysical Research Communications
Volume345
Issue number2
DOIs
Publication statusPublished - Jun 30 2006

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Hemopexin
Heme
Oxidation
Kinetics
Peroxynitrous Acid
Poisons

Keywords

  • Ferrous hemopexin-heme nitrosylation
  • Nitrate formation
  • O-mediated oxidation of ferrous nitrosylated hemopexin-heme
  • Rabbit hemopexin

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

Cite this

O2-mediated oxidation of hemopexin-heme(II)-NO. / Fasano, Mauro; Antonini, Giovanni; Ascenzi, Paolo.

In: Biochemical and Biophysical Research Communications, Vol. 345, No. 2, 30.06.2006, p. 704-712.

Research output: Contribution to journalArticle

Fasano, Mauro ; Antonini, Giovanni ; Ascenzi, Paolo. / O2-mediated oxidation of hemopexin-heme(II)-NO. In: Biochemical and Biophysical Research Communications. 2006 ; Vol. 345, No. 2. pp. 704-712.
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abstract = "Hemopexin (HPX), serving as scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. Here, kinetics of HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO are reported. NO reacts reversibly with HPX-heme(II) yielding HPX-heme(II)-NO, according to the minimum reaction scheme:{A formula is presented}values of kon, koff, and K (=kon/koff) are (6.3 ± 0.3) × 103 M-1 s-1, (9.1 ± 0.4) × 10-4 s-1, and (6.9 ± 0.6) × 106 M-1, respectively, at pH 7.0 and 10.0 °C. O2 reacts with HPX-heme(II)-NO yielding HPX-heme(III) and multiscripts(NO, mml:none(), mml:none(), 3, -), by means of the ferric heme-bound peroxynitrite intermediate (HPX-heme(III)-N(O)OO), according to the minimum reaction scheme:{A formula is presented}the backward reaction rate is negligible. Values of hon and l are (2.4 ± 0.3) × 101 M-1 s-1 and (1.4 ± 0.2) × 10-3 s-1, respectively, at pH 7.0 and 10.0 °C. The decay of HPX-heme(III)-N(O)OO (i.e., l) is rate limiting. The HPX-heme(III)-N(O)OO intermediate has been characterized by optical absorption spectroscopy in the Soret region (λmax = 409 nm and ε409 = 1.51 × 105 M-1 cm-1). These results, representing the first kinetic evidence for HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO, might be predictive of transient (pseudo-enzymatic) function(s) of heme carriers.",
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AU - Antonini, Giovanni

AU - Ascenzi, Paolo

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N2 - Hemopexin (HPX), serving as scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. Here, kinetics of HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO are reported. NO reacts reversibly with HPX-heme(II) yielding HPX-heme(II)-NO, according to the minimum reaction scheme:{A formula is presented}values of kon, koff, and K (=kon/koff) are (6.3 ± 0.3) × 103 M-1 s-1, (9.1 ± 0.4) × 10-4 s-1, and (6.9 ± 0.6) × 106 M-1, respectively, at pH 7.0 and 10.0 °C. O2 reacts with HPX-heme(II)-NO yielding HPX-heme(III) and multiscripts(NO, mml:none(), mml:none(), 3, -), by means of the ferric heme-bound peroxynitrite intermediate (HPX-heme(III)-N(O)OO), according to the minimum reaction scheme:{A formula is presented}the backward reaction rate is negligible. Values of hon and l are (2.4 ± 0.3) × 101 M-1 s-1 and (1.4 ± 0.2) × 10-3 s-1, respectively, at pH 7.0 and 10.0 °C. The decay of HPX-heme(III)-N(O)OO (i.e., l) is rate limiting. The HPX-heme(III)-N(O)OO intermediate has been characterized by optical absorption spectroscopy in the Soret region (λmax = 409 nm and ε409 = 1.51 × 105 M-1 cm-1). These results, representing the first kinetic evidence for HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO, might be predictive of transient (pseudo-enzymatic) function(s) of heme carriers.

AB - Hemopexin (HPX), serving as scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. Here, kinetics of HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO are reported. NO reacts reversibly with HPX-heme(II) yielding HPX-heme(II)-NO, according to the minimum reaction scheme:{A formula is presented}values of kon, koff, and K (=kon/koff) are (6.3 ± 0.3) × 103 M-1 s-1, (9.1 ± 0.4) × 10-4 s-1, and (6.9 ± 0.6) × 106 M-1, respectively, at pH 7.0 and 10.0 °C. O2 reacts with HPX-heme(II)-NO yielding HPX-heme(III) and multiscripts(NO, mml:none(), mml:none(), 3, -), by means of the ferric heme-bound peroxynitrite intermediate (HPX-heme(III)-N(O)OO), according to the minimum reaction scheme:{A formula is presented}the backward reaction rate is negligible. Values of hon and l are (2.4 ± 0.3) × 101 M-1 s-1 and (1.4 ± 0.2) × 10-3 s-1, respectively, at pH 7.0 and 10.0 °C. The decay of HPX-heme(III)-N(O)OO (i.e., l) is rate limiting. The HPX-heme(III)-N(O)OO intermediate has been characterized by optical absorption spectroscopy in the Soret region (λmax = 409 nm and ε409 = 1.51 × 105 M-1 cm-1). These results, representing the first kinetic evidence for HPX-heme(II) nitrosylation and O2-mediated oxidation of HPX-heme(II)-NO, might be predictive of transient (pseudo-enzymatic) function(s) of heme carriers.

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