阿尔法-1,4-葡萄糖酶通过核性移位进行转移消除,然后进行同同消除
Seung Seo Lee1, Shukun Yu, Stephen G Withers
1Department of Chemistry, Protein Engineering Network of Centres of Excellence of Canada, University of British Columbia, Vancouver, BC Canada V6T 1Z1.
Journal of the American Chemical Society
|May 2, 2002
概括
阿尔法-葡萄糖酶 (GLase) 使用合成消除机制,通过捕获一种糖酶中间体来确认. 这种中间体涉及Asp 553,并释放1,5-d-无水果糖.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 碳水化合物化学 碳水化合物化学
背景情况:
- 阿尔法-葡萄糖酶 (GLase) 催化阿尔法-1,4-葡萄糖键的分裂.
- GLase的反应机制一直是研究的主题.
研究的目的:
- 阐明阿尔法-葡萄糖酶 (GLase) 的催化机制.
- 为了确定参与催化过程的关键氨基酸残留物.
- 要区分拟议的消除机制.
主要方法:
- 使用5--β-l-异酸,一个α-葡萄糖酶失活剂,GLAase的失活.
- 捕获的葡萄糖酶中间体的分离和表征.
- 通过序列分析识别核氨基酸残留物.
- 使用替代基质的动态同位素效应研究.
主要成果:
- GLase被禁用,并成功地捕获了稳定的糖酶中间体.
- 在位置553 (Asp 553) 的酸被确定为核性残留物,保存在相关的α-glucosidases中.
- 该中间体经历同排泄反应,产生产物1,5-d-无水果糖.
- 在C2缺少一次性动态同位素效应,这表明对转移消除机制.
结论:
- GLase的催化机制涉及一个同同消除通路.
- Asp 553对于催化至关重要,形成一个共价中间体.
- 这些发现澄清了GLase的反应途径及其与其他α-glucosidases的关系.
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