Structural and biochemical analyses of shikimate dehydrogenase AroE from Aquifex aeolicus:: Implications for the catalytic mechanism
Structural and biochemical analyses of shikimate dehydrogenase AroE from Aquifex aeolicus:: Implications for the catalytic mechanism
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DOI：
10.1021/bi602601e
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发表时间：
2007-08-21
期刊：
影响因子：
2.9
通讯作者：
Ji, Xinhua
中科院分区：
文献类型：
--
作者：
Gan, Jianhua;Wu, Yan;Ji, Xinhua
莽草酸生物合成途径对微生物、植物和寄生虫是必需的，但在哺乳动物中不存在。因此，莽草酸脱氢酶（SD）和该途径中的其他酶是开发无毒抗菌药物、除草剂和抗寄生虫药物的有吸引力的靶点。SD催化途径中的第四个反应，即3-脱氢莽草酸至莽草酸（SA）的烟酰胺腺嘌呤二核苷酸磷酸（NADP-）依赖性还原，以及通过氢化物的转移进行的逆转。以前的结构研究表明，酶存在于两个主要的构象，开放和封闭的形式。为了使反应发生，据信催化络合物呈现闭合构象。然而，含有SA和NADP（+）的唯一结构表现出开放构象（PDB条目2 EV 9）。在这里，我们提出了两种晶体结构的Aquifex aeolicus SD，包括三元复合物与SA和NADP（+），假设封闭的构象，因此包含一个催化活性位点。在已有的和新的结构和生化数据的基础上，提出了一种催化机制。
The shikimate biosynthetic pathway is essential to microorganisms, plants, and parasites but absent from mammals. Therefore, shikimate dehydrogenase (SD) and other enzymes in the pathway are attractive targets for developing nontoxic antimicrobial agents, herbicides, and antiparasite drugs. SD catalyzes the fourth reaction in the pathway, the nicotinamide adenine dinucleotide phosphate- (NADP-) dependent reduction of 3-dehydroshikimic acid to shikimic acid (SA), as well as its reverse, by the transfer of a hydride. Previous structural studies reveal that the enzyme exists in two major conformations, an open and a closed form. For the reaction to occur, it is believed that the catalytic complex assumes the closed conformation. Nonetheless, the only structure containing both SA and NADP(+) exhibits an open conformation (PDB entry 2EV9). Here, we present two crystal structures of Aquifex aeolicus SD, including a ternary complex with both SA and NADP(+), which assumes the closed conformation and therefore contains a catalytically competent active site. On the basis of preexisting and novel structural and biochemical data, a catalytic mechanism is proposed.