Enzymatic properties of human hemalbumin
Enzymatic properties of human hemalbumin
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DOI：
10.1016/s0167-4838(01)00192-3
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发表时间：
2001-06-11
期刊：
影响因子：
--
通讯作者：
Galliano, M
中科院分区：
文献类型：
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作者：
Monzani, E;Bonafè, B;Galliano, M
使用 UV-Vis、CD 和 NMR 技术重新研究了氯高铁血红素与人血清白蛋白 (HSA) 初级位点的结合。结合血红素的主要部分含有五配位的高自旋铁 (III) 中心，但一小部分金属似乎处于六配位的低自旋状态，其中有一个“远端”残基，可能是第二个组氨酸残基。完成协调范围。加合物的还原铁 (II) 形式含有六配位低自旋血红素。远端残基阻碍了叠氮化物和氰化物等小阴离子配体进入血红素-HSA 的铁 (III) 中心，并破坏了中性双原子 (如双氧和一氧化碳) 与铁 (II) 形式的结合。尽管存在这些限制，血红素-HSA 复合物仍能促进过氧化氢活化过程，该过程具有酶促反应的特征，并且可能具有生物学相关性。该复合物实际上能够催化与酪氨酸和过氧化氢歧化相关的酚类化合物的过氧化反应。动力学和机理研究证实，过氧化过程发生的低效率取决于过氧化氢和铁（III）中心之间形成活性物质的有限反应速率以及竞争性过氧化物降解反应。 (C) 2001 Elsevier Science B.V. 保留所有权利。
The binding of hemin to the primary site of human serum albumin (HSA) has been reinvestigated using UV-Vis, CD and NMR techniques. The major fraction of bound hemin contains a five-coordinated high-spin iron(III) center, but a minor fraction of the metal appears to be in a six-coordinated, low-spin state, where a 'distal' residue, possibly a second histidine residue. completes the coordination sphere. The reduced, iron(II) form of the adduct contains six-coordinated low-spin heme. The distal residue hinders the access to the iron(III) center of hemin-HSA to small anionic ligands like azide and cyanide and destabilizes the binding of neutral diatomics like dioxygen and carbon monoxide to the iron(II) form. In spite of these limitations, the hemin-HSA complex promotes hydrogen peroxide activation processes that bear the characteristics of enzymatic reactions and may have biological relevance. The complex is in fact capable of catalyzing peroxidative reactions on phenolic compounds related to tyrosine and hydrogen peroxide dismutation. Kinetic and mechanistic studies confirm that the low efficiency with which peroxidative processes occur depends on the limited rate of the reaction between hydrogen peroxide and the iron(III) center, to form the active species, and by the competitive peroxide degradation reaction. (C) 2001 Elsevier Science B.V. All rights reserved.