High dissociation rate constant of ferrous-dioxy complex linked to the catalase-like activity in lactoperoxidase

Semira Galijasevic, Ghassan M. Saed, Michael Peter Diamond, Husam M. Abu-Soud

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O2 at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O 2 was first order and monophasic and with rate constants k on = 3.8 × 104 M-1 S-1 and koff = 11.2 s-1. The dissociation rate constant for the formation of LPO-Fe(II)-O2 is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O2 linkage. Our results have also shown that the decay of the LPO-Fe(II)-O 2 complex occurs by two sequential O2-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O2 linkage with a rate constant of 0.5 s-1. The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s-1. A comprehensive kinetic model that links LPO-Fe(II)-O2 complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.

Original languageEnglish (US)
Pages (from-to)39465-39470
Number of pages6
JournalJournal of Biological Chemistry
Volume279
Issue number38
DOIs
StatePublished - Sep 17 2004

Fingerprint

Lactoperoxidase
Catalase
Rate constants
Heme
Superoxides
Ligands
Kinetics
Geometry
Enzymes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

High dissociation rate constant of ferrous-dioxy complex linked to the catalase-like activity in lactoperoxidase. / Galijasevic, Semira; Saed, Ghassan M.; Diamond, Michael Peter; Abu-Soud, Husam M.

In: Journal of Biological Chemistry, Vol. 279, No. 38, 17.09.2004, p. 39465-39470.

Research output: Contribution to journalArticle

@article{a3c80dfcbe91405ba0817173f6a91122,
title = "High dissociation rate constant of ferrous-dioxy complex linked to the catalase-like activity in lactoperoxidase",
abstract = "Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O2 at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O 2 was first order and monophasic and with rate constants k on = 3.8 × 104 M-1 S-1 and koff = 11.2 s-1. The dissociation rate constant for the formation of LPO-Fe(II)-O2 is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O2 linkage. Our results have also shown that the decay of the LPO-Fe(II)-O 2 complex occurs by two sequential O2-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O2 linkage with a rate constant of 0.5 s-1. The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s-1. A comprehensive kinetic model that links LPO-Fe(II)-O2 complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.",
author = "Semira Galijasevic and Saed, {Ghassan M.} and Diamond, {Michael Peter} and Abu-Soud, {Husam M.}",
year = "2004",
month = "9",
day = "17",
doi = "10.1074/jbc.M406003200",
language = "English (US)",
volume = "279",
pages = "39465--39470",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "38",

}

TY - JOUR

T1 - High dissociation rate constant of ferrous-dioxy complex linked to the catalase-like activity in lactoperoxidase

AU - Galijasevic, Semira

AU - Saed, Ghassan M.

AU - Diamond, Michael Peter

AU - Abu-Soud, Husam M.

PY - 2004/9/17

Y1 - 2004/9/17

N2 - Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O2 at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O 2 was first order and monophasic and with rate constants k on = 3.8 × 104 M-1 S-1 and koff = 11.2 s-1. The dissociation rate constant for the formation of LPO-Fe(II)-O2 is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O2 linkage. Our results have also shown that the decay of the LPO-Fe(II)-O 2 complex occurs by two sequential O2-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O2 linkage with a rate constant of 0.5 s-1. The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s-1. A comprehensive kinetic model that links LPO-Fe(II)-O2 complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.

AB - Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O2 at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O 2 was first order and monophasic and with rate constants k on = 3.8 × 104 M-1 S-1 and koff = 11.2 s-1. The dissociation rate constant for the formation of LPO-Fe(II)-O2 is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O2 linkage. Our results have also shown that the decay of the LPO-Fe(II)-O 2 complex occurs by two sequential O2-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O2 linkage with a rate constant of 0.5 s-1. The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s-1. A comprehensive kinetic model that links LPO-Fe(II)-O2 complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.

UR - http://www.scopus.com/inward/record.url?scp=4544348224&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4544348224&partnerID=8YFLogxK

U2 - 10.1074/jbc.M406003200

DO - 10.1074/jbc.M406003200

M3 - Article

C2 - 15258136

AN - SCOPUS:4544348224

VL - 279

SP - 39465

EP - 39470

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 38

ER -