Chang C S, Yamazaki I, Sinclair R, Khalid S, Powers L
National Center for the Design of Molecular Function, Utah State University, Logan 84322-4630.
Biochemistry. 1993 Jan 26;32(3):923-8. doi: 10.1021/bi00054a025.
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 A at pH 7, decreasing to 1.72 +/- 0.02 A 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.
我们使用X射线吸收光谱法，在两个不同的pH值下研究了辣根过氧化物酶（HRP）化合物II的活性位点。结果表明，活性位点第六个配位配体的键长在pH 7时为1.90±0.02 Å，在pH 10时降至1.72±0.02 Å。铁与吡咯氮以及近端配体的平均键长没有显著变化。铁中心周围高配位壳层的位置发生了变化，这意味着附近的氨基酸残基和/或血红素发生了一些移动或变形。本研究结果表明，在较高pH值下HRP化合物II的Fe-O键长减小可能归因于pH 7时氧配体与血红素口袋中一个氨基酸残基之间存在的氢键的丧失。
