The oxidized (3,3) state of manganese catalase. Comparison of enzymes from Thermus thermophilus and Lactobacillus plantarum.
The oxidized (3,3) state of manganese catalase. Comparison of enzymes from Thermus thermophilus and Lactobacillus plantarum.
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锰过氧化氢酶的氧化 (3,3) 态。
DOI：
10.1021/bi990499d
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Whittaker,JW
中科院分区：
文献类型：
--
作者：
Whittaker,MM;Barynin,VV;Antonyuk,SV;Whittaker,JW
锰过氧化氢酶含有双核锰簇，其催化过氧化氢的氧化还原歧化，在周转期间在二锰（II）[（2，2）]和二锰（III）[（3，3）]氧化态之间相互转化。我们利用光学吸收、CD、MCD和EPR光谱作为活性中心金属簇的电子结构和蛋白质环境的灵敏探针，研究了来自嗜热栖热菌和植物乳杆菌的同源酶的氧化（3，3）态。比较这两种酶的结果，可以识别活性位点的基本特征，并确定差异。对于这两种酶，具有最高催化活性的制剂具有抗磁性基态，与晶体学上定义的双-μ-桥接二锰核心结构一致。氧化损伤和外源性配体结合扰乱LPC的核心结构，将酶转化为不同的形式，其中簇由于桥连配体介导的交换偶联改变而变得顺磁性。TTC簇对配体结合没有表现出这种敏感性，这意味着该酶中的桥具有不同的反应性。提出了一种机制，涉及酶周转的两个半反应中过氧化物底物的不同配位模式。
Manganese catalases contain a binuclear manganese cluster that catalyzes the redox dismutation of hydrogen peroxide, interconverting between dimanganese(II) [(2,2)] and dimanganese(III) [(3,3)] oxidation states during turnover. We have investigated the oxidized (3,3) states of the homologous enzymes fromThermus thermophilusandLactobacillus plantarumusing a combination of optical absorption, CD, MCD, and EPR spectroscopies as sensitive probes of the electronic structure and protein environment for the active site metal clusters. Comparison of results for these two enzymes allows the essential features of the active sites to be recognized and the differences identified. For both enzymes, preparations having the highest catalytic activity have diamagnetic ground states, consistent with the bis-μ-bridging dimanganese core structure that has been defined crystallographically. Oxidative damage and exogenous ligand binding perturb the core structure of LPC, converting the enzyme to a distinct form in which the cluster becomes paramagnetic as a result of altered exchange coupling mediated by the bridging ligands. The TTC cluster does not exhibit this sensitivity to ligand binding, implying a different reactivity for the bridges in that enzyme. A mechanism is proposed involving distinct coordination modes for peroxide substrate in each of the two half-reactions for enzyme turnover.