Crystal structure of a raw-starch-degrading bacterial α-amylase belonging to subfamily 37 of the glycoside hydrolase family GH13.
Crystal structure of a raw-starch-degrading bacterial α-amylase belonging to subfamily 37 of the glycoside hydrolase family GH13.
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属于糖苷水解酶家族 GH13 亚家族 37 的生淀粉降解细菌 α-淀粉酶的晶体结构
DOI：
10.1038/srep44067
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发表时间：
2017-03-17
影响因子：
4.6
通讯作者：
He C
中科院分区：
文献类型：
--
作者：
Liu Y;Yu J;Li F;Peng H;Zhang X;Xiao Y;He C
糖苷水解酶家族GH 13的第37个亚家族是最近在海洋宏基因组文库中发现的一种新型α-淀粉酶（AmyP）的基础上建立的。AmyP具有原淀粉降解活性，由N端催化结构域和C端淀粉结合结构域组成。为了了解这个最新的亚家族，我们确定了与麦芽糖复合的AmyP催化结构域的晶体结构，命名为AmyPΔSBD，以及与麦芽三糖复合的E221 Q突变体AmyPΔSBD的晶体结构。Glu 221是三个保守的催化残基之一，AmyP通过E221 Q突变而失活。AmyPΔSBD的结构域B形成从结构域A突出的环，稳定活性位点的构象并增加酶的热稳定性。一个新的钙离子位于邻近的-3亚位点结合环，并可能是负责增加的热稳定性的酶后，加入钙。此外，Tyr 36参与与亚位点-3处的糖基序的堆积和氢键相互作用。本研究首次揭示了GH 13亚家族37 α-淀粉酶的结构，为合理设计α-淀粉酶突变体提供了理论依据。
Subfamily 37 of the glycoside hydrolase family GH13 was recently established on the basis of the discovery of a novel α-amylase, designated AmyP, from a marine metagenomic library. AmyP exhibits raw-starch-degrading activity and consists of an N-terminal catalytic domain and a C-terminal starch-binding domain. To understand this newest subfamily, we determined the crystal structure of the catalytic domain of AmyP, named AmyPΔSBD, complexed with maltose, and the crystal structure of the E221Q mutant AmyPΔSBD complexed with maltotriose. Glu221 is one of the three conserved catalytic residues, and AmyP is inactivated by the E221Q mutation. Domain B of AmyPΔSBD forms a loop that protrudes from domain A, stabilizes the conformation of the active site and increases the thermostability of the enzyme. A new calcium ion is situated adjacent to the -3 subsite binding loop and may be responsible for the increased thermostability of the enzyme after the addition of calcium. Moreover, Tyr36 participates in both stacking and hydrogen bonding interactions with the sugar motif at subsite -3. This work provides the first insights into the structure of α-amylases belonging to subfamily 37 of GH13 and may contribute to the rational design of α-amylase mutants with enhanced performance in biotechnological applications.