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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Modes of heme binding and substrate access for cytochrome P450 CYP74A revealed by crystal structures of allene oxide synthase
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Modes of heme binding and substrate access for cytochrome P450 CYP74A revealed by crystal structures of allene oxide synthase

机译：丙二烯氧化合酶的晶体结构揭示了细胞色素P450 CYP74A的血红素结合和底物接近模式

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摘要

Cytochrome P450s exist ubiquitously in all organisms and are involved in many biological processes. Allene oxide synthase (AOS) is a P450 enzyme that plays a key role in the biosynthesis of oxylipin jasmonates, which are involved in signal and defense reactions in higher plants. The crystal structures of guayule (Parthenium argentatum) AOS (CYP74A2) and its complex with the substrate analog 13(S)-hydroxyoctadeca-9Z,11E-dienoic acid have been determined. The structures exhibit a classic P450 fold but possess a heme-binding mode with an unusually long heme binding loop and a unique l-helix. The structures also reveal two channels through which substrate and product may access and leave the active site. The entrances are defined by a loop between β3-2 and β3-3. Asn-276 in the substrate binding site may interact with the substrate's hydroperoxy group and play an important role in catalysis, and Lys-282 at the entrance may control substrate access and binding. These studies provide both structural insights into AOS and related P450s and a structural basis to understand the distinct reaction mechanism.
机译：细胞色素P450普遍存在于所有生物中，并参与许多生物过程。烯丙氧化物合酶（AOS）是一种P450酶，在茉莉素脂的生物合成中起关键作用，茉莉脂酸酯的茉莉酸酯参与高等植物的信号和防御反应。已经确定了愈创木（Athylene guayatum）AOS（CYP74A2）的晶体结构及其与底物类似物13（S）-hydroxyoctadeca-9Z，11E-dienoic acid的配合物。该结构表现出经典的P450折叠，但具有血红素结合模式，具有异常长的血红素结合环和独特的l螺旋。该结构还揭示了两个通道，底物和产物可通过两个通道进入和离开活性部位。入口由β3-2和β3-3之间的循环定义。底物结合位点中的Asn-276可能与底物的氢过氧基相互作用，并在催化中起重要作用，而入口处的Lys-282可能控制底物的进入和结合。这些研究提供了对AOS和相关P450的结构见解，并为理解独特的反应机理提供了结构基础。

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