pH Dependence of the Active Site of Horseradish Peroxidase Compound II

C. S. Chang, I. Yamazaki, R. Sinclair, S. Khalid, L. Powers

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38 Scopus citations


Using X-ray absorption spectroscopy, we investigated the active site of horseradish peroxidase (HRP) compound II at two different pH values. The results indicate that the bond length of the sixth coordinated ligand of the active site was 1.90 ± 0.02 Å at pH 7, decreasing to 1.72 ± 0.02 Å at pH 10. The average iron-to-pyrrole nitrogen and the proximal ligand bond lengths showed no significant changes. The position of higher coordination shells around the iron center changed, implying that some movement or deformation of nearby amino acid residues and/or of the heme occurred. Results of this study suggest that the decrease of the Fe-O bond length of HRP compound II at the higher pH might be attributed to the loss of a hydrogen bond which is present between the oxygen ligand and an amino acid residue in the heme pocket at pH 7.

Original languageEnglish (US)
Pages (from-to)923-928
Number of pages6
Issue number3
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry


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