Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands
The kinetics of azide and fluoride binding to various monomeric and tetrameric ferric hemoproteins (sperm whale Mb, isolated α and β chains of human Hb reacted with p ‐chloromercuribenzoate, dromedary, ox and human Hb) has been investigated (at pH 6.5 and 20°C) over a large range (20 μM to 2 M) of l...
Published in: | European Journal of Biochemistry |
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crwiley:10.1111/j.1432-1033.1996.00049.x 2024-06-02T08:14:54+00:00 Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands Coletta, Massimo Angeletti, Mauro De Sanctis, Giampiero Cerroni, Loredana Giardina, Bruno Amiconi, Gino Ascenzi, Paolo 1996 http://dx.doi.org/10.1111/j.1432-1033.1996.00049.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1432-1033.1996.00049.x https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1996.00049.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor European Journal of Biochemistry volume 235, issue 1-2, page 49-53 ISSN 0014-2956 1432-1033 journal-article 1996 crwiley https://doi.org/10.1111/j.1432-1033.1996.00049.x 2024-05-03T11:03:56Z The kinetics of azide and fluoride binding to various monomeric and tetrameric ferric hemoproteins (sperm whale Mb, isolated α and β chains of human Hb reacted with p ‐chloromercuribenzoate, dromedary, ox and human Hb) has been investigated (at pH 6.5 and 20°C) over a large range (20 μM to 2 M) of ligand concentration. It has been observed that the pseudo‐first‐order rate constant for azide binding to the hemoproteins investigated does not increase linearly with ligand concentration, but tends to level off toward an asymptotic concentration‐independent value typical for each hemoprotein. This behaviour, which has been detected only by an investigation covering an unusually large range of ligand concentrations, appears to be independent of the ionic strength, and it underlies the existence of a rate‐limiting step in the dynamic pathway of azide binding to ferric hemoproteins, which is detectable whenever the observed pseudo‐first‐order rate constant becomes faster than a given value characteristic of the specific hemoprotein. Such a behaviour is not observed in the case of fluoride binding probably because the pseudo‐first‐order rate constant for this ligand is much slower and never attains a value faster than that of the rate‐limiting step. In general terms, this feature should involve a conformational equilibrium between at least two forms (possibly related to the interaction of H 2 O with distal histidine and its exchange with the bulk solvent) which modulates the access of the anionic ligand into the heme pocket and its reaction with the ferric heme iron. Article in Journal/Newspaper Sperm whale Wiley Online Library Dromedary ENVELOPE(163.033,163.033,-78.317,-78.317) European Journal of Biochemistry 235 1-2 49 53 |
institution |
Open Polar |
collection |
Wiley Online Library |
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crwiley |
language |
English |
description |
The kinetics of azide and fluoride binding to various monomeric and tetrameric ferric hemoproteins (sperm whale Mb, isolated α and β chains of human Hb reacted with p ‐chloromercuribenzoate, dromedary, ox and human Hb) has been investigated (at pH 6.5 and 20°C) over a large range (20 μM to 2 M) of ligand concentration. It has been observed that the pseudo‐first‐order rate constant for azide binding to the hemoproteins investigated does not increase linearly with ligand concentration, but tends to level off toward an asymptotic concentration‐independent value typical for each hemoprotein. This behaviour, which has been detected only by an investigation covering an unusually large range of ligand concentrations, appears to be independent of the ionic strength, and it underlies the existence of a rate‐limiting step in the dynamic pathway of azide binding to ferric hemoproteins, which is detectable whenever the observed pseudo‐first‐order rate constant becomes faster than a given value characteristic of the specific hemoprotein. Such a behaviour is not observed in the case of fluoride binding probably because the pseudo‐first‐order rate constant for this ligand is much slower and never attains a value faster than that of the rate‐limiting step. In general terms, this feature should involve a conformational equilibrium between at least two forms (possibly related to the interaction of H 2 O with distal histidine and its exchange with the bulk solvent) which modulates the access of the anionic ligand into the heme pocket and its reaction with the ferric heme iron. |
format |
Article in Journal/Newspaper |
author |
Coletta, Massimo Angeletti, Mauro De Sanctis, Giampiero Cerroni, Loredana Giardina, Bruno Amiconi, Gino Ascenzi, Paolo |
spellingShingle |
Coletta, Massimo Angeletti, Mauro De Sanctis, Giampiero Cerroni, Loredana Giardina, Bruno Amiconi, Gino Ascenzi, Paolo Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
author_facet |
Coletta, Massimo Angeletti, Mauro De Sanctis, Giampiero Cerroni, Loredana Giardina, Bruno Amiconi, Gino Ascenzi, Paolo |
author_sort |
Coletta, Massimo |
title |
Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
title_short |
Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
title_full |
Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
title_fullStr |
Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
title_full_unstemmed |
Kinetic Evidence for the Existence of a Rate‐Limiting Step in the Reaction of Ferric Hemoproteins with Anionic Ligands |
title_sort |
kinetic evidence for the existence of a rate‐limiting step in the reaction of ferric hemoproteins with anionic ligands |
publisher |
Wiley |
publishDate |
1996 |
url |
http://dx.doi.org/10.1111/j.1432-1033.1996.00049.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1432-1033.1996.00049.x https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1996.00049.x |
long_lat |
ENVELOPE(163.033,163.033,-78.317,-78.317) |
geographic |
Dromedary |
geographic_facet |
Dromedary |
genre |
Sperm whale |
genre_facet |
Sperm whale |
op_source |
European Journal of Biochemistry volume 235, issue 1-2, page 49-53 ISSN 0014-2956 1432-1033 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1432-1033.1996.00049.x |
container_title |
European Journal of Biochemistry |
container_volume |
235 |
container_issue |
1-2 |
container_start_page |
49 |
op_container_end_page |
53 |
_version_ |
1800738902626009088 |