"Back door" opening implied by the crystal structure of a carbamoylated acetylcholinesterase
"Back door" opening implied by the crystal structure of a carbamoylated acetylcholinesterase
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DOI：
10.1021/bi982723p
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发表时间：
1999-05-04
期刊：
影响因子：
2.9
通讯作者：
Lamba, D
中科院分区：
文献类型：
--
作者：
Bartolucci, C;Perola, E;Lamba, D
本文报道了毒扁豆碱类似物8-（cis-2，6-dimethylmorpholino）octylcarbamoyleseroline（MF 268）氨甲酰化的加利福尼亚电鳐（Torpedocalfornica，Tc）乙酰胆碱酯酶（AChE）的晶体结构。在X射线结构中，MF 268的二甲基吗啉辛基氨基甲酸部分与催化丝氨酸共价结合，该丝氨酸位于狭长峡谷的底部。抑制剂的烷基链填充在峡谷的上部，阻挡了活性位点的入口。令人惊讶的是，在晶体结构中没有发现相对大体积的eseroline，因此意味着存在另一种清除它的途径。这代表了可能发生“后门”打开的间接证据，并表明通过“后门”释放产物是该酶的可能替代物。然而，就底物水解机制而言，其相关性需要确定。这项研究表明，使用适当设计的酰化抑制剂，它可以阻止入口的催化位点，可以利用作为一种通用的方法来调查存在的“后门”的清除产品。
The crystal structure of Torpedo californica (Tc) acetylcholinesterase (AChE) carbamoylated by the physostigmine analogue 8-(cis-2,6-dimethylmorpholino)octylcarbamoyleseroline (MF268) is reported at 2.7 Angstrom resolution. In the X-ray structure, the dimethylmorpholinooctylcarbamic moiety of MF268 is covalently bound to the catalytic serine, which is located at the bottom of a long and narrow gorge. The alkyl chain of the inhibitor fills the upper part of the gorge, blocking the entrance of the active site. This prevents eseroline, the leaving group of the carbamoylation process, from exiting through this path. Surprisingly, the relatively bulky eseroline is not found in the crystal structure, thus implying the existence of an alternative route for its clearance. This represents indirect evidence that a "back door" opening may occur and shows that the release of products via a "back door" is a likely alternative for this enzyme. However, its relevance as far as the mechanism of substrate hydrolysis is concerned needs to be established. This study suggests that the use of properly designed acylating inhibitors, which can block the entrance of catalytic sites, may be exploited as a general approach for investigating the existence of "back doors" for the clearance of products.