额外的盐桥可提高 1,4-α-葡聚糖分支酶的热稳定性。
Additional salt bridges improve the thermostability of 1,4-α-glucan branching enzyme.
机构信息
School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
出版信息
Food Chem. 2020 Jun 30;316:126348. doi: 10.1016/j.foodchem.2020.126348. Epub 2020 Feb 3.
The 1,4-α-glucan branching enzyme from Geobacillus thermoglucosidans STB02 (GtGBE, EC 2.4.1.18) does not possess the thermostability required by modified starch industry. To increase its thermostability, a rational design strategy was used to introduce additional salt bridges into GtGBE. The strategy involved in mutation of individual residues to form "local" two-residue salt bridges. Accordingly, five of local salt bridges (Q231R-D227, Q231K-D227, T339E-K335, T339D-K335, and I571D-R569 mutants) were separately introduced into GtGBE. The half-times of these mutants at 60 °C were 17% to 51% longer than that of wild-type. Subsequently, these two-residue salt bridges were extended to form salt bridge networks (Q231R/K-D227-D131H, T339D/E-K335-I291H, and I571D-R569-R617H mutants). Among these mutants, except I571D-R569-R617H, the half-times of Q231R/K-D227-D131H, T339D/E-K335-I291H mutants at 60 °C were 15%, 17%, 21% and 17% longer than those of the corresponding two-residue salt bridges, respectively. The results showed that design and introduction of salt bridges improves enzyme thermostability in GtGBE.
来自嗜热解糖梭菌 STB02 的 1,4-α-葡聚糖分支酶（GtGBE，EC 2.4.1.18）不具备改性淀粉工业所需的热稳定性。为了提高其热稳定性，采用合理的设计策略在 GtGBE 中引入额外的盐桥。该策略涉及突变单个残基以形成“局部”二残基盐桥。因此，将五个局部盐桥（Q231R-D227、Q231K-D227、T339E-K335、T339D-K335 和 I571D-R569 突变体）分别引入 GtGBE。这些突变体在 60°C 时的半衰期比野生型长 17%至 51%。随后，这些二残基盐桥扩展形成盐桥网络（Q231R/K-D227-D131H、T339D/E-K335-I291H 和 I571D-R569-R617H 突变体）。在这些突变体中，除了 I571D-R569-R617H 外，Q231R/K-D227-D131H、T339D/E-K335-I291H 突变体在 60°C 时的半衰期分别比相应的二残基盐桥长 15%、17%、21%和 17%。结果表明，在 GtGBE 中设计和引入盐桥可以提高酶的热稳定性。
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