The occurrence of riboflavin kinase and FAD synthetase ensures FAD synthesis in tobacco mitochondria and maintenance of cellular redox status
The occurrence of riboflavin kinase and FAD synthetase ensures FAD synthesis in tobacco mitochondria and maintenance of cellular redox status
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DOI：
10.1111/j.1742-4658.2008.06775.x
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发表时间：
2009-01-01
期刊：
影响因子：
5.4
通讯作者：
Barile, Maria
中科院分区：
文献类型：
--
作者：
Giancaspero, Teresa A.;Locato, Vittoria;Barile, Maria
从烟草中分离的完整线粒体。亮黄2（TBY-2）细胞可以通过载体介导的系统摄取核黄素，该系统在不同的浓度范围内运行，并具有不同的摄取效率。一旦进入线粒体，由于线粒体核黄素激酶（EC 2.7.1.26）和FAD合成酶（EC 2.7.7.2）的存在，核黄素被转化为催化活性辅因子FMN和FAD。新合成的FAD可以从完整的线粒体通过一个推定的FAD输出。FMN合成速率对核黄素浓度的依赖性显示出S形的饱和动力学（S = 0.5，V-max和希尔系数值分别为0.32 +/-0.12 μ m，1.4 nmol·min（-1）·mg（-1）蛋白质和3.1）。FAD形成酶都被MgCl 2激活，并且存在于两种不同的单功能酶中，其可以分别在线粒体可溶性和膜富集级分中物理分离。
Intact mitochondria isolated from Nicotiana tabacum cv. Bright Yellow 2 (TBY-2) cells can take up riboflavin via carrier-mediated systems that operate at different concentration ranges and have different uptake efficiencies. Once inside mitochondria, riboflavin is converted into catalytically active cofactors, FMN and FAD, due to the existence of a mitochondrial riboflavin kinase (EC 2.7.1.26) and an FAD synthetase (EC 2.7.7.2). Newly synthesized FAD can be exported from intact mitochondria via a putative FAD exporter. The dependence of FMN synthesis rate on riboflavin concentration shows saturation kinetics with a sigmoidal shape (S-0.5, V-max and Hill coefficient values 0.32 +/- 0.12 mu m, 1.4 nmol.min(-1).mg(-1) protein and 3.1, respectively). The FAD-forming enzymes are both activated by MgCl2, and reside in two distinct monofunctional enzymes, which can be physically separated in mitochondrial soluble and membrane-enriched fractions, respectively.