来自Flavobacterium johnsoniae的GH97葡萄糖脱酶对α-(1→6) 结合偏好的结构洞察
Shuntaro Nakamura1, Rikuya Kurata2, Takatsugu Miyazaki1,2,3
1Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, Japan.
The FEBS journal
|April 25, 2024
概括
这项研究揭示了细菌酶Flavobacterium johnsoniae glucodextranase (FjGH97A) 如何区分α-(1→6) 和α-(1→4) 葡萄糖酸链接. 在酶中的关键氨基酸Ala195
科学领域:
- 酶学和蛋白质结构-功能关系.
- 微生物碳水化合物代谢和酶特异性.
- 甘氨酸酸酶家族97 (GH97) 的特征.
背景情况:
- 糖化酶家族97 (GH97) 酶表现出多种基质特异性,包括异位逆转α-糖化酶和异位保留α-化酶.
- Flavobacterium johnsoniae glucodextranase (FjGH97A) 是一种GH97酶,向德克斯中的α-(1→6) - 葡萄糖酸结合,与其他喜欢α-(1→4) - 结合的SusB等GH97酶形成鲜明对比.
研究的目的:
- 阐明FjGH97A基质特异性的结构基础,特别是它更喜欢α-(1→6) 而不是α-(1→4) 的葡萄糖结合.
- 为了确定特定的氨基酸残留物,负责确定GH97酶家族内的链接特异性.
主要方法:
- 确定FjGH97A与葡萄糖,泛糖和异三糖复合的结晶结构.
- 进行了FjGH97A的局部定向突变发生,专注于活性部位的残留物,包括Ala195和Ile378.
- 评估了野生类型和突变FjGH97A酶对α-(1→4) 和α-(1→6) -葡萄糖酸键的基质偏好.
主要成果:
- 结构分析显示FjGH97A中保留了催化残留物,类似于其他异构逆转GH97酶.
- 与SusB的比较突出了活跃部位子部位+1和+2的差异,特别是FjGH97A中的Ala195和Ile378.
- 突变A195S和A195S-I378F显示了基质特异性的改变,对α-(1→4) - 葡萄糖酸结合的活性增加,这意味着Ala195在结合偏好.
结论:
- 氨基酸残留物Ala195,位于保存循环-N上,在确定FjGH97A.FjGH97A.的α-(1→6) 链接特异性方面发挥着至关重要的作用.
- 了解GH97酶中的这些特异性决定因素,可以了解微生物碳水化合物利用途径.
- 这些发现凸显了特定活性位点残留在决定糖化酶家族内的酶功能的重要性.
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