Chloroperoxidase-catalyzed epoxidation of cis-β-methylstyrene: distal pocket flexibility tunes catalytic reactivity.
Chloroperoxidase-catalyzed epoxidation of cis-β-methylstyrene: distal pocket flexibility tunes catalytic reactivity.
复制标题
氯过氧化物酶催化的顺-β-甲基苯乙烯环氧化：远端口袋灵活性调节催化反应性。
DOI：
10.1021/jp302763h
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Chatfield,DavidC
中科院分区：
文献类型：
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作者：
Morozov,AlexanderN;Chatfield,DavidC
氯过氧化物酶是最通用的血红素蛋白，具有与过氧化物酶和细胞色素 P450 具有相同结构特征的混合活性位点袋。这里提出的模拟研究表明，该酶具有有效利用其混合结构的显着能力，假定结构不同的过氧化物酶样和 P450 样远端口袋面，从而增强活性中心的固有催化能力。我们发现，在顺式-β-甲基苯乙烯（CBMS）的环氧化过程中，随着极性 Glu183 侧链远离活性中心，远端口袋的天然过氧化物酶样方面会减弱，并且远端口袋呈现出更具疏水性的 P450 样方面。类似 P450 的远端口袋为 14 kcal/mol 反应势垒提供了约 4 kcal/mol 的显着焓稳定，用于氧化铁基血红素硫醇盐对 CMBS 的气相环氧化。这种稳定性来自远端口袋的呼吸。由于直到最近，氯过氧化物酶的活性位点还被认为是不灵活的，这些结果表明了对该酶多功能性的新概念理解：催化反应性是通过远端口袋的灵活性来调节的。
Chloroperoxidase, the most versatile heme protein, has a hybrid active site pocket that shares structural features with peroxidases and cytochrome P450s. The simulation studies presented here show that the enzyme possesses a remarkable ability to efficiently utilize its hybrid structure, assuming structurally different peroxidase-like and P450-like distal pocket faces and thereby enhancing the inherent catalytic capability of the active center. We find that, during epoxidation ofcis-β-methylstyrene (CBMS), the native peroxidase-like aspect of the distal pocket is diminished as the polar Glu183 side chain is displaced away from the active center and the distal pocket takes on a more hydrophobic, P450-like, aspect. The P450-like distal pocket provides a significant enthalpic stabilization of ∼4 kcal/mol of the 14 kcal/mol reaction barrier for gas-phase epoxidation of CMBS by an oxyferryl heme-thiolate species. This stabilization comes from breathing of the distal pocket. As until recently the active site of chloroperoxidase was postulated to be inflexible, these results suggest a new conceptual understanding of the enzyme’s versatility: catalytic reactivity is tuned by flexibility of the distal pocket.