Active site modulation in the N-acetylneuraminate lyase sub-family as revealed by the structure of the inhibitor-complexed Haemophilus influenzae enzyme
Active site modulation in the N-acetylneuraminate lyase sub-family as revealed by the structure of the inhibitor-complexed Haemophilus influenzae enzyme
复制标题
DOI：
10.1006/jmbi.2000.4138
复制
发表时间：
2000-10-27
影响因子：
5.6
通讯作者：
Lawrence, MC
中科院分区：
文献类型：
--
作者：
Barbosa, JARG;Smith, BJ;Lawrence, MC
n -乙酰神经氨酸解酶（NAL）亚家族的（β / α）(8)酶具有共同的催化步骤，但在不同的生物途径中催化反应。已知的例子包括NAL、二氢二吡啶酸合成酶（DHDPS）、d -5-酮-4-脱氧葡萄糖酸脱水酶、2-酮-3-脱氧葡萄糖酸醛缩酶、反式-羟基苄基丙酮酸水解醛缩酶和反式-2'-羧基苯丙酮酸水解酶醛缩酶。对于在亚家族中调节各自活性位点的三维结构以实现同源底物识别的方式知之甚少。我们在这里展示了流感嗜血杆菌NAL的结构，通过x射线晶体学测定，最大分辨率为1.60埃，以天然形式和与三种底物类似物（唾液酸糖醇，4-脱氧唾液酸和4-氧唾液酸）的复合物存在。这些结构首次揭示了NAL活性位点完整底物的结合模式。在上述结构、底物复合DHDPS结构和跨亚族序列比较的基础上，我们能够提出一个统一的有源位点调制模型。该模型是一种经济的模型，允许在适当的地方保留或重新定位与结合共同底物取代基相关的残基。我们的结构还表明，在亚家族的所有活性位点发现的严格保守的酪氨酸残基的作用，即它在底物辅助催化反应途径中介导α -酮酸羧酸的质子提取。(C) 2000年学术出版社。
The N-acetylneuraminate lyase (NAL) sub-family of (beta/alpha)(8) enzymes share a common catalytic step but catalyse reactions in different biological pathways. Known examples include NAL, dihydrodipicolinate synthetase (DHDPS), D-5-keto-4-deoxyglucarate dehydratase, 2-keto-3-deoxygluconate aldolase, trans-o-hydroxybenzylidenepyruvate hydrolasealdolase and trans-2'-carboxybenzalpyruvate hydratase-aldolase. Little is known about the way in which the three-dimensional structure of the respective active sites are modulated across the sub-family to achieve cognate substrate recognition. We present here the structure of Haemophilus influenzae NAL determined by X-ray crystallography to a maximum resolution of 1.60 Angstrom, in native form and in complex with three substrate analogues (sialic acid alditol, 4-deoxy-sialic acid and 4-oxo-sialic acid). These structures reveal for the first time the mode of binding of the complete substrate in the NAL active site. On the basis of the above structures, that of substrate-complexed DHDPS and sequence comparison across the sub-family we are able to propose a unified model for active site modulation. The model is one of economy, allowing wherever appropriate the retention or relocation of residues associated with binding common substrate substituent groups. Our structures also suggest a role for the strictly conserved tyrosine residue found in all active sites of the sub-family, namely that it mediates proton abstraction by the alpha -keto acid carboxylate in a substrate-assisted catalytic reaction pathway. (C) 2000 Academic Press.