IDENTIFICATION OF A GLOBIN FREE-RADICAL IN EQUINE MYOGLOBIN TREATED WITH PEROXIDES
IDENTIFICATION OF A GLOBIN FREE-RADICAL IN EQUINE MYOGLOBIN TREATED WITH PEROXIDES
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DOI：
10.1016/0167-4838(91)90529-9
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发表时间：
1991-03-08
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影响因子：
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通讯作者：
DAVIES, MJ
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作者：
DAVIES, MJ
高铁肌红蛋白 (MetMb) 与 H2O2 反应生成一种类似于过氧化物酶化合物 II 的 Ferryl 物质，并且比初始水平高出一个氧化当量。过氧化物的第二氧化当量迅速转移到周围的蛋白质中，产生蛋白质自由基。先前的研究表明，该基团以芳香残基（可能是酪氨酸）为中心，但不允许明确指定。该自由基的身份已使用停流 EPR 进行了研究。马 MetMb 与等摩尔 H2O2 的反应产生 6 线信号，g 为 2.0044，耦合常数约为 2.0044。 α-H 2.26 和 α-2H 0.75 mT，以及第二个广泛的基础信号。两个信号都迅速衰减。多重信号的参数与空间受限的酪氨酸苯氧基自由基的存在一致。该自由基与 O2、H2O2 和许多其他底物进一步反应。这一活性，以及仅在 Tyr-103 残基处碘化的 MetMb 未检测到此类物质的观察结果表明，该物质是由易于接近的 Tyr-103 残基（靠近血红素中心）而不是更远的埋藏的 Tyr-146 残基产生的。该苯氧基自由基与氧反应生成酪氨酸过氧自由基，该酪氨酸过氧自由基先前已被自旋陷阱 DMPO 捕获。
Reaction of metmyoglobin (MetMb) with H2O2 generates a ferryl species which is analogous to Compound II of peroxidases and is one oxidising equivalent above the initial level. The second oxidising equivalent from the peroxide is rapidly transferred into the surrounding protein generating a protein radical. Previous studies have suggested that this radical is centered on an aromatic residue, probably a tyrosine, but have not allowed unambiguous assignment. The identity of this radical has been investigated using stopped flow EPR. Reaction of equine MetMb with equimolar H2O2 gives a 6-line signal with g 2.0044 and coupling constants approx. alpha-H 2.26 and alpha-2H 0.75 mT, together with a second, broad, underlying signal. Both signals decay rapidly. The parameters of the multiplet signal are consistent with the presence of a sterically constrained tyrosine phenoxyl radical. This radical reacts further with O2, H2O2 and a number of other substrates. This activity, together with the observation that such a species is not detected with MetMb which has been iodinated solely at the Tyr-103 residue, suggests that this species is being generated from the readily accessible Tyr-103 residue, which is near the haem centre, rather than the more distant, buried, Tyr-146 residue. Reaction of this phenoxyl radical with oxygen gives the tyrosine peroxyl radical which has been previously trapped with the spin trap DMPO.