Atomic structure of plant glutamine synthetase - A key enzyme for plant productivity
Atomic structure of plant glutamine synthetase - A key enzyme for plant productivity
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DOI：
10.1074/jbc.m601497200
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发表时间：
2006-09-29
影响因子：
4.8
通讯作者：
Kusunoki, Masami
中科院分区：
文献类型：
--
作者：
Unno, Hideaki;Uchida, Tatsuya;Kusunoki, Masami
植物作为食物链中唯一的初级生产者，为动物和其他异养生物提供营养。谷氨酰胺合成酶（Glutamine Synthetase，GS）是植物自养过程中必需的酶之一，它催化氨与谷氨酸结合生成谷氨酰胺，并伴随ATP水解，在植物生长发育过程中各种代谢过程中产生的氨的同化和再同化中起着重要作用。阐明高等植物GS的原子结构对于理解其详细的反应机理以及进一步了解植物生产力和农学用途是重要的。本文报道了玉米（Zea mays L.）GS.该结构揭示了一种独特的十聚体结构，与细菌GS结构显著不同。高等植物具有几种GS同工酶，它们在热稳定性和催化特性方面不同，以有效地响应环境和营养的变化。在GS 1a中，发现负责热稳定性的关键残基是Ile-161。这三种结构与底物类似物，包括广泛使用的除草剂膦丝菌素复合，使我们提出了一种磷酸盐从ATP转移到谷氨酸的机制，并解释了膦丝菌素的抑制作用，作为开发新的潜在除草剂的指导。
Plants provide nourishment for animals and other heterotrophs as the sole primary producer in the food chain. Glutamine synthetase (GS), one of the essential enzymes for plant autotrophy catalyzes the incorporation of ammonia into glutamate to generate glutamine with concomitant hydrolysis of ATP, and plays a crucial role in the assimilation and re-assimilation of ammonia derived from a wide variety of metabolic processes during plant growth and development. Elucidation of the atomic structure of higher plant GS is important to understand its detailed reaction mechanism and to obtain further insight into plant productivity and agronomical utility. Here we report the first crystal structures of maize (Zea mays L.) GS. The structure reveals a unique decameric structure that differs significantly from the bacterial GS structure. Higher plants have several isoenzymes of GS differing in heat stability and catalytic properties for efficient responses to variation in the environment and nutrition. A key residue responsible for the heat stability was found to be Ile-161 in GS1a. The three structures in complex with substrate analogues, including phosphinothricin, a widely used herbicide, lead us to propose a mechanism for the transfer of phosphate from ATP to glutamate and to interpret the inhibitory action of phosphinothricin as a guide for the development of new potential herbicides.