人类二氧化原酶中的基质蛋白相互作用:H76的关键作用
Dipanwita Batabyal1, Syun-Ru Yeh
1Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, usa.
Journal of the American Chemical Society
|February 13, 2009
概括
在人类二氧化三二氧化酶 (hTDO) 中研究histidine 76 (H76) 揭示了其作为活性基位基的关键作用. 突变H76S和H76A通过破坏催化和基质结合,显著损害了酶活性.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 蛋白质科学 蛋白质科学
背景情况:
- kynurenine 途径始于托氧化,这是一个由 hTDO 和 hIDO 催化的关键步骤.
- 在htDO中的histidine 76 (H76) 被假设为活性基位基,对于托 (Trp) 氧化至关重要.
- 在hIDO中的同类残留物是氨酸,表明功能分歧.
研究的目的:
- 阐明人类二氧化二二氧化酶 (hTDO) 中保存的H76残留物的功能和结构意义.
- 通过局部定向突变发生的hTDO的催化机制和基质结合的研究.
主要方法:
- 使用局部导向的突变发生法来产生HTDO的H76S和H76A突变.
- 进行了酶活性测定以确定动力参数 (kcat和KM).
- 共振拉曼光谱法与托类型被用于探测活性位点相互作用.
主要成果:
- 无论是H76S还是H76A突变,都导致催化效率 (kcat) 降低,基质亲和力 (KM) 增加.
- 减少kcat的原因是H76基催化剂的丧失,取而代之的是水等较弱的催化物种.
- 增加的KM表明H76有助于特定的基质-蛋白相互作用和基质在活性位点内的定位.
结论:
- H76残留物对hTDO的催化活性和基质结合都至关重要.
- 突变H76破坏了活性位点内的复杂相互作用网络,影响了酶的整体功能.
- 这些发现强调了H76在稳定活性三元复合物 (l-Trp-O2-hTDO) 中的重要性.
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