Meso-Unsubstituted Iron Corrole in Hemoproteins: Remarkable Differences in Effects on Peroxidase Activities between Myoglobin and Horseradish Peroxidase
Meso-Unsubstituted Iron Corrole in Hemoproteins: Remarkable Differences in Effects on Peroxidase Activities between Myoglobin and Horseradish Peroxidase
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DOI：
10.1021/ja907428e
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发表时间：
2009-10-28
影响因子：
15
通讯作者：
Hayashi, Takashi
中科院分区：
文献类型：
--
作者：
Matsuo, Takashi;Hayashi, Akihiro;Hayashi, Takashi
肌红蛋白 (Mb) 和辣根过氧化物酶 (HRP) 均用内消旋未取代的铁咔咯重构，并研究了它们的电子构型和过氧化物酶活性。铁咔咯并入 apoMb 后出现的 540 nm 条带表明 Mb 血红素口袋中近端组氨酸咪唑的轴向协调。基于使用埃文斯法的 (1)H NMR 测量，铁咔咯重构 Mb 的总磁化率评估为 S = 3/2。相反，虽然在将铁咔咯重构到HRP基质中的过程中，在540nm附近没有出现谱带，但在添加连二亚硫酸盐时观察到与铁咔咯重构的Mb相似的光谱。这一观察结果表明重构的 HRP 中咔咯铁的氧化态可以指定为 +4。两种蛋白对愈创木酚氧化的催化活性截然不同；铁咔咯重构的HRP可减缓愈创木酚的H(2)O(2)依赖性氧化，而铁咔咯重构的Mb催化的相同反应则具有相反的作用并加速该反应。这一发现可归因于当这些蛋白质处于静息状态时，咔咯铁的氧化态存在差异。
Myoglobin (Mb) and horseradish peroxidase (HRP) were both reconstituted with a meso-unsubstituted iron corrole and their electronic configurations and peroxidase activities were investigated. The appearance of the 540 nm band upon incorporation of the iron corrole into apoMb indicates axial coordination by the proximal histidine imidazole in the Mb heme pocket. Based on (1)H NMR measurements using the Evans method, the total magnetic susceptibility of the iron corrole reconstituted Mb was evaluated to be S = 3/2. In contrast, although a band does not appear in the vicinity of 540 nm during reconstitution of the iron corrole into the matrix of HRP, a spectrum similar to that of the iron corrole reconstituted Mb is observed upon the addition of dithionite. This observation suggests that the oxidation state of the corrole iron in the reconstituted HRP can be assigned as +4. The catalytic activities of both proteins toward guaiacol oxidation are quite different; the iron corrole reconstituted HRP decelerates H(2)O(2)-dependent oxidation of guaiacol, while the same reaction catalyzed by iron corrole reconstituted Mb has the opposite effect and accelerates the reaction. This finding can be attributed to the difference in the oxidation states of the corrole iron when these proteins are in the resting state.