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 language | English |
|---|---|
| Pages (from-to) | 704-712 |
| Number of pages | 9 |
| Journal | Biochemical and Biophysical Research Communications |
| Volume | 345 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Jun 30 2006 |
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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 journal › Article
}
TY - JOUR
T1 - O2-mediated oxidation of hemopexin-heme(II)-NO
AU - Fasano, Mauro
AU - Antonini, Giovanni
AU - Ascenzi, Paolo
PY - 2006/6/30
Y1 - 2006/6/30
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.
KW - Ferrous hemopexin-heme nitrosylation
KW - Nitrate formation
KW - O-mediated oxidation of ferrous nitrosylated hemopexin-heme
KW - Rabbit hemopexin
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UR - http://www.scopus.com/inward/citedby.url?scp=33646836457&partnerID=8YFLogxK
U2 - 10.1016/j.bbrc.2006.04.154
DO - 10.1016/j.bbrc.2006.04.154
M3 - Article
C2 - 16696943
AN - SCOPUS:33646836457
VL - 345
SP - 704
EP - 712
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -