GDP-mannose-3',5'-epimerase的结构和功能:一种在同一活性部位进行三种化学反应的酶
Louise L Major1, Beata A Wolucka, James H Naismith
1Centre for Biomolecular Sciences, University of St. Andrews, North Haugh, St. Andrews, Fife, Scotland KY16 9ST, United Kingdom.
Journal of the American Chemical Society
|December 22, 2005
概括
阿拉比多普西斯塔利亚纳 GDP-曼诺-3
科学领域:
- 生物化学 生物化学
- 结构生物学 结构生物学
- 植物科学 植物科学
背景情况:
- 在植物中,GDP-mannose-3',5'-epimerase (GME) 对于维生素C的生物合成至关重要.
- GME催化了GDP-alpha-D-mannose的转化为GDP-beta-L-galactose的过程.
- 该酶还产生GDP-β-L-糖,一种C5'表皮.
研究的目的:
- 阐明GME的催化机制的结构基础.
- 为了理解GDP-alpha-D-mannose的双重表皮化.
- 为了研究该酶在维生素C合成中的作用.
主要方法:
- GME复合体与基质和产品的X射线晶体学.
- 位点定向的突变发生,以确定关键的催化残留物.
- 生物化学测试以确认酶活性和产品形成.
主要成果:
- 确定了GME复合体的高分辨率结构,揭示了经典的短链脱酶/还原酶 (SDR) 折叠.
- 确认GME在GDP-β-L-银和GDP-β-L-糖之间建立了平衡.
- 确定了一对催化酸/基 (C145和K217) 负责表皮化.
- 提出了一种反应机制,涉及C4'氧化,C5'表皮化,随后还原或C3'表皮化.
结论:
- GME利用一个单一的活性部位进行氧化,表皮化和还原,这是一个不寻常的催化策略.
- 结构洞察力表明在催化过程中存在特定的中间体和构造变化.
- 这些发现为植物维生素C生物合成的关键步骤提供了详细的分子理解.
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