Resonance Raman spectra of horseradish peroxidase and bovine liver catalase compound I species. Evidence for predominant 2A(2u) π-cation radical ground state configurations

Woei-Jer Chuang, H. E. Van Wart

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

The nature of the porphyrin π-cation radicals in the horseradish peroxidase and bovine liver catalase (BLC) compound I species have been investigated by studying their resonance Raman spectra. A variety of laser excitation and sample interrogation procedures have been employed in order to minimize previously documented problems arising from photoinduced conversions. With Soret band excitation, the spectra obtained for both species resemble that of a compound II-like photoproduct unless the samples are excited with residence times in the microsecond regime with very low (~1 milliwatt) powers. When these precautions are taken, spectra attributable to the compound I species themselves are obtained. The spectrum for horseradish peroxidase compound I is similar to that reported by Paeng and Kincaid (Paeng, K.-J., and Kincaid, J. R. (1988) Am. Chem. Soc. 110, 7913-7915) using a similar approach. Both horseradish peroxidase and BLC compound I exhibit frequency shifts relative to their compound II species that are in the direction observed for model π-cation radicals with predominant 2A(2u) character. The magnitudes of these shifts are smaller than those observed for heme models that lack aromatic axial ligands, but agree well with those observed on formation of the compound I analog of N(α)-acetyl microperoxidase-8 that has His as a proximal ligand. This observation is consistent with partial delocalization of the radical density onto the proximal His-170 and Tyr-357 ligands in horseradish peroxidase and BLC, respectively. The strong ligand field provided by these ligands on the proximal side and oxo ligand on the distal side of the heme group is apparently sufficient to reverse the 2A(1u) radical ground state preference observed for heme-like porphyrin species (e.g. octaethylporphyrins) with weak axial fields. Enhancement of several bands assigned to the Tyr-357 ligand has also been observed for BLC compound I with 406.7-nm excitation. This is attributed either to resonance with a tyrosinate → Fe(IV) charge transfer band or to the coupling provided by radical spin delocalization onto the tyrosinate ligand.

Original languageEnglish
Pages (from-to)13293-13301
Number of pages9
JournalJournal of Biological Chemistry
Volume267
Issue number19
Publication statusPublished - 1992 Jan 1

Fingerprint

Horseradish Peroxidase
Liver
Catalase
Ground state
Cations
Raman scattering
Ligands
Heme
Porphyrins
Laser excitation
catalase I
Charge transfer
Lasers

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

@article{a5bc7057cafb4d158efbbb9954f0c822,
title = "Resonance Raman spectra of horseradish peroxidase and bovine liver catalase compound I species. Evidence for predominant 2A(2u) π-cation radical ground state configurations",
abstract = "The nature of the porphyrin π-cation radicals in the horseradish peroxidase and bovine liver catalase (BLC) compound I species have been investigated by studying their resonance Raman spectra. A variety of laser excitation and sample interrogation procedures have been employed in order to minimize previously documented problems arising from photoinduced conversions. With Soret band excitation, the spectra obtained for both species resemble that of a compound II-like photoproduct unless the samples are excited with residence times in the microsecond regime with very low (~1 milliwatt) powers. When these precautions are taken, spectra attributable to the compound I species themselves are obtained. The spectrum for horseradish peroxidase compound I is similar to that reported by Paeng and Kincaid (Paeng, K.-J., and Kincaid, J. R. (1988) Am. Chem. Soc. 110, 7913-7915) using a similar approach. Both horseradish peroxidase and BLC compound I exhibit frequency shifts relative to their compound II species that are in the direction observed for model π-cation radicals with predominant 2A(2u) character. The magnitudes of these shifts are smaller than those observed for heme models that lack aromatic axial ligands, but agree well with those observed on formation of the compound I analog of N(α)-acetyl microperoxidase-8 that has His as a proximal ligand. This observation is consistent with partial delocalization of the radical density onto the proximal His-170 and Tyr-357 ligands in horseradish peroxidase and BLC, respectively. The strong ligand field provided by these ligands on the proximal side and oxo ligand on the distal side of the heme group is apparently sufficient to reverse the 2A(1u) radical ground state preference observed for heme-like porphyrin species (e.g. octaethylporphyrins) with weak axial fields. Enhancement of several bands assigned to the Tyr-357 ligand has also been observed for BLC compound I with 406.7-nm excitation. This is attributed either to resonance with a tyrosinate → Fe(IV) charge transfer band or to the coupling provided by radical spin delocalization onto the tyrosinate ligand.",
author = "Woei-Jer Chuang and {Van Wart}, {H. E.}",
year = "1992",
month = "1",
day = "1",
language = "English",
volume = "267",
pages = "13293--13301",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "19",

}

TY - JOUR

T1 - Resonance Raman spectra of horseradish peroxidase and bovine liver catalase compound I species. Evidence for predominant 2A(2u) π-cation radical ground state configurations

AU - Chuang, Woei-Jer

AU - Van Wart, H. E.

PY - 1992/1/1

Y1 - 1992/1/1

N2 - The nature of the porphyrin π-cation radicals in the horseradish peroxidase and bovine liver catalase (BLC) compound I species have been investigated by studying their resonance Raman spectra. A variety of laser excitation and sample interrogation procedures have been employed in order to minimize previously documented problems arising from photoinduced conversions. With Soret band excitation, the spectra obtained for both species resemble that of a compound II-like photoproduct unless the samples are excited with residence times in the microsecond regime with very low (~1 milliwatt) powers. When these precautions are taken, spectra attributable to the compound I species themselves are obtained. The spectrum for horseradish peroxidase compound I is similar to that reported by Paeng and Kincaid (Paeng, K.-J., and Kincaid, J. R. (1988) Am. Chem. Soc. 110, 7913-7915) using a similar approach. Both horseradish peroxidase and BLC compound I exhibit frequency shifts relative to their compound II species that are in the direction observed for model π-cation radicals with predominant 2A(2u) character. The magnitudes of these shifts are smaller than those observed for heme models that lack aromatic axial ligands, but agree well with those observed on formation of the compound I analog of N(α)-acetyl microperoxidase-8 that has His as a proximal ligand. This observation is consistent with partial delocalization of the radical density onto the proximal His-170 and Tyr-357 ligands in horseradish peroxidase and BLC, respectively. The strong ligand field provided by these ligands on the proximal side and oxo ligand on the distal side of the heme group is apparently sufficient to reverse the 2A(1u) radical ground state preference observed for heme-like porphyrin species (e.g. octaethylporphyrins) with weak axial fields. Enhancement of several bands assigned to the Tyr-357 ligand has also been observed for BLC compound I with 406.7-nm excitation. This is attributed either to resonance with a tyrosinate → Fe(IV) charge transfer band or to the coupling provided by radical spin delocalization onto the tyrosinate ligand.

AB - The nature of the porphyrin π-cation radicals in the horseradish peroxidase and bovine liver catalase (BLC) compound I species have been investigated by studying their resonance Raman spectra. A variety of laser excitation and sample interrogation procedures have been employed in order to minimize previously documented problems arising from photoinduced conversions. With Soret band excitation, the spectra obtained for both species resemble that of a compound II-like photoproduct unless the samples are excited with residence times in the microsecond regime with very low (~1 milliwatt) powers. When these precautions are taken, spectra attributable to the compound I species themselves are obtained. The spectrum for horseradish peroxidase compound I is similar to that reported by Paeng and Kincaid (Paeng, K.-J., and Kincaid, J. R. (1988) Am. Chem. Soc. 110, 7913-7915) using a similar approach. Both horseradish peroxidase and BLC compound I exhibit frequency shifts relative to their compound II species that are in the direction observed for model π-cation radicals with predominant 2A(2u) character. The magnitudes of these shifts are smaller than those observed for heme models that lack aromatic axial ligands, but agree well with those observed on formation of the compound I analog of N(α)-acetyl microperoxidase-8 that has His as a proximal ligand. This observation is consistent with partial delocalization of the radical density onto the proximal His-170 and Tyr-357 ligands in horseradish peroxidase and BLC, respectively. The strong ligand field provided by these ligands on the proximal side and oxo ligand on the distal side of the heme group is apparently sufficient to reverse the 2A(1u) radical ground state preference observed for heme-like porphyrin species (e.g. octaethylporphyrins) with weak axial fields. Enhancement of several bands assigned to the Tyr-357 ligand has also been observed for BLC compound I with 406.7-nm excitation. This is attributed either to resonance with a tyrosinate → Fe(IV) charge transfer band or to the coupling provided by radical spin delocalization onto the tyrosinate ligand.

UR - http://www.scopus.com/inward/record.url?scp=0026681590&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0026681590&partnerID=8YFLogxK

M3 - Article

VL - 267

SP - 13293

EP - 13301

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 19

ER -