International Journal of Biological Macromolecules
International Journal of Biological Macromolecules
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国际生物大分子杂志
DOI：
10.1016/j.ijbiomac.2017.01.086
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发表时间：
2017-05-01
影响因子：
8.2
通讯作者：
Naeem, Aabgeena
中科院分区：
文献类型：
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作者：
Abidi, Minhal;Iram, Afshin;Naeem, Aabgeena
黑曲霉（Aspergillusniger）的葡糖淀粉酶（3.2.1.3）具有31%的α-螺旋结构、36%的β-螺旋结构和其余的非周期结构。采用多种方法研究了葡萄糖淀粉酶在不同浓度乙二醛（GO）和三氟乙醇（TFE）存在下的结构转变。在20%GO下，葡糖淀粉酶以熔融球状态存在，如通过高色氨酸和ANS荧光、二级结构的保留和天然三级结构的损失所证明的。该状态在聚集过程开始之前，并且在最高浓度即90%的GO下达到最大值。在平行研究中，当浓度增加至25%时，TFE诱导二级结构转化，导致分子间13片层的积累，改变色氨酸环境，高ANS和ThT荧光，导致葡糖淀粉酶聚集体的形成。等温滴定量热曲线呈S形，表明GO/TFE与糖化酶的结合较弱。透射电镜研究表明，葡萄糖淀粉酶在90%乙二醛和25%TFE时分别以球形和无定形聚集体存在。此外，70%的TFE导致酶聚集体的抑制;在该浓度下观察到的大多数二级结构是螺旋。α螺旋是主要的关键参与者，如通过CD、FTIR和TEM所证实的，其使葡糖淀粉酶天然环境重新定位。因此，6折叠的诱导促进蛋白质聚集，而α螺旋抑制蛋白质聚集。(C)2017爱思唯尔B. V.保留所有权利。
Glucoamylase (EC 3.2.1.3) from Aspergillus niger possesses 31% alpha-helix, 36% beta structure and rest aperiodic structure. A transition of glucoamylase structure in the presence of varying concentrations of glyoxal (GO) and trifluoroethanol (TFE) was studied by using multi-methodological approaches. At 20% GO, glucoamylase exists as molten globule state as evident by high tryptophan and ANS fluorescence, retention of secondary structure and loss of native tertiary structure. This state precedes the onset of the aggregation process and maximum is achieved at the highest concentration i.e. at 90% of GO. In parallel study TFE, on increasing concentration up to 25% induces secondary structure transformation leading to accumulation of intermolecular 13 sheets, altered tryptophan environment, high ANS and ThT fluorescence resulting in the formation of glucoamylase aggregates. Isothermal titration calorimetric curve is sigmoidal, indicating the weak binding of GO/TFE and glucoamylase. TEM studies showed that glucoamylase exists as globular and amorphous aggregates at 90% glyoxal and 25% TFE respectively. Further, TFE at 70% causes inhibition of enzyme aggregates; the majority of secondary structures observed at this concentration are a helices. Alpha helices being the main key player relocates glucoamylase native environment as evident by CD, FTIR and TEM. Hence induction of 6 sheet promotes protein aggregation and a helices inhibits protein aggregation. (C) 2017 Elsevier B.V. All rights reserved.