Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands

Massimo Coletta, Mauro Angeletti, Giampiero De Sanctis, Loredana Cerroni, Bruno Giardina, Gino Amiconi, Paolo Ascenzi

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

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 H2O 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.

Original languageEnglish
Pages (from-to)49-53
Number of pages5
JournalEuropean Journal of Biochemistry
Volume235
Issue number1-2
Publication statusPublished - 1996

Fingerprint

Azides
Ligands
Kinetics
Rate constants
Heme
Fluorides
Sperm Whale
Chloromercuribenzoates
Camelus
Ionic strength
Histidine
Osmolar Concentration
Iron

Keywords

  • azide binding
  • conformational transition
  • ferric hemoproteins
  • kinetics

ASJC Scopus subject areas

  • Biochemistry

Cite this

Coletta, M., Angeletti, M., De Sanctis, G., Cerroni, L., Giardina, B., Amiconi, G., & Ascenzi, P. (1996). Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands. European Journal of Biochemistry, 235(1-2), 49-53.

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.

In: European Journal of Biochemistry, Vol. 235, No. 1-2, 1996, p. 49-53.

Research output: Contribution to journalArticle

Coletta, M, Angeletti, M, De Sanctis, G, Cerroni, L, Giardina, B, Amiconi, G & Ascenzi, P 1996, 'Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands', European Journal of Biochemistry, vol. 235, no. 1-2, pp. 49-53.
Coletta M, Angeletti M, De Sanctis G, Cerroni L, Giardina B, Amiconi G et al. Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands. European Journal of Biochemistry. 1996;235(1-2):49-53.
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. In: European Journal of Biochemistry. 1996 ; Vol. 235, No. 1-2. pp. 49-53.
@article{8a506243114a4b7f8616faa42b5f9beb,
title = "Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands",
abstract = "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 H2O 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.",
keywords = "azide binding, conformational transition, ferric hemoproteins, kinetics",
author = "Massimo Coletta and Mauro Angeletti and {De Sanctis}, Giampiero and Loredana Cerroni and Bruno Giardina and Gino Amiconi and Paolo Ascenzi",
year = "1996",
language = "English",
volume = "235",
pages = "49--53",
journal = "European Journal of Biochemistry",
issn = "0014-2956",
publisher = "Wiley-Blackwell",
number = "1-2",

}

TY - JOUR

T1 - Kinetic evidence for the existence of a rate-limiting step in the reaction of ferric hemoproteins with anionic ligands

AU - Coletta, Massimo

AU - Angeletti, Mauro

AU - De Sanctis, Giampiero

AU - Cerroni, Loredana

AU - Giardina, Bruno

AU - Amiconi, Gino

AU - Ascenzi, Paolo

PY - 1996

Y1 - 1996

N2 - 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 H2O 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.

AB - 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 H2O 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.

KW - azide binding

KW - conformational transition

KW - ferric hemoproteins

KW - kinetics

UR - http://www.scopus.com/inward/record.url?scp=0030042056&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030042056&partnerID=8YFLogxK

M3 - Article

VL - 235

SP - 49

EP - 53

JO - European Journal of Biochemistry

JF - European Journal of Biochemistry

SN - 0014-2956

IS - 1-2

ER -