一种非催化氨酸残留物调节了人类B12处理酶CblC的可巴胺反应性
Anna J Esser1, Santiago Sastre2,3,4, Thien-Ly Julia Dinh5
1Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, Freiburg im Breisgau 79106, Germany.
Biochemistry
|January 25, 2025
概括
在CblC酶处理维生素B12. 人类CblC中的一种特定的氨酸残留物 (Cys149) 似乎微调了它的反应性,影响了电子转移和氨酸稳定性,特别是在富含氧气的环境中.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 维生素B12的新陈代谢
背景情况:
- 人类CblC对于加工食维生素B12至关重要,涉及连接体去除和缩.
- 在CblC中,有5种囊类残留物,Cys149的功能以前是未知的.
- Cys149在哺乳动物中保存,这表明它可能在CblC活动中发挥重要作用.
研究的目的:
- 研究保存的Cys149残留物在人类CblC功能中的作用.
- 确定Cys149如何影响CblC的催化活性和反应机制.
- 为了比较野生类型CblC的活性与缺乏或在Cys149.9改变的工程变体.
主要方法:
- 人工CblC变体 (Cys149Ser和Cys149Ala) 是为了研究Cys149.9的作用而创建的.
- 使用谷氨驱动的甲基可巴胺脱基化 (MeCbl) 来测量反应速率.
- 氧化谷氨 (GSSG) 的终点确定评估了电子转移解.
- 随着时间的推移,特别是在有氧条件下,对可巴胺物种 (aquacobalamin, cob(II) 进行了监测.
主要成果:
- 与野生型CblC相比,将Cys149转变为Ser或Ala导致MeCbl的脱基化率更快.
- 突变者表现出显著的未合电子转移,导致氧化谷氨酸的形成增加.
- 在氧气的存在下,突变体显示了水果胺转化为cob (II) 胺,与野生型CblC不同.
- 在突变者中观察到的更快的脱基化速率是以更慢的速率常数为代价的.
结论:
- 人类CblC中的Cys149通过最大限度地减少未合的电子转移和在有氧条件下稳定cob(II) 胺来调整催化活性.
- 149的存在导致反应更慢,更受控制,在氧气较高或可胺周转需求较低的环境中可能有利.
- 这些发现表明CblC功能与氧气供应和代谢需求相关的进化适应,与C. elegans的CblC相似.
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