In Rhodobacter sphaeroides respiratory nitrate reductase, the kinetics of substrate binding favors intramolecular electron transfer
In Rhodobacter sphaeroides respiratory nitrate reductase, the kinetics of substrate binding favors intramolecular electron transfer
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DOI：
10.1021/ja0384072
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发表时间：
2004-02-11
影响因子：
15
通讯作者：
Léger, C
中科院分区：
文献类型：
--
作者：
Frangioni, B;Arnoux, P;Léger, C
呼吸道硝酸还原酶（NapAB）来源于Rb.类球蛋白酶是属于DMSO还原酶家族的含有周质胞浆的酶。我们报告的NapAB蛋白膜伏安法（PFV）的研究，我们提出了第一个定量解释的复杂的氧化还原状态的依赖性的活动，也已观察到与其他相关的酶。我们用来拟合数据的模型假设，结合的基板部分限制营业额和更快，更弱的Mo离子时，在V氧化态比当它是完全还原。我们解释了如何在催化循环中的存在下，这种缓慢的化学步骤耦合到活性位点的电子转移减少所需的驱动力，以减少MoVion，并使放能的最后一个分子内的电子转移步骤（之间的近端立方烷和Mo辅因子）。重要的是，比较与所有钼酶PFV数据可用，我们强调的能量学的DMSO还原酶家族的酶的催化循环的一般特征。
The respiratory nitrate reductase (NapAB) fromRb. sphaeroidesis a periplasmic molybdenum-containing enzyme which belongs to the DMSO reductase family. We report a study of NapAB by protein film voltammetry (PFV), and we present the first quantitative interpretation of the complex redox-state dependence of activity that has also been observed with other related enzymes. The model we use to fit the data assumes that binding of substrate partly limits turnover and is faster and weaker when the Mo ion is in the V oxidation state than when it is fully reduced. We explain how the presence in the catalytic cycle of such slow chemical steps coupled to electron transfer to the active site decreases the driving force required to reduce the MoVion and makes exergonic the last intramolecular electron-transfer step (between the proximal cubane and the Mo cofactor). Importantly, comparison is made with all Mo enzymes for which PFV data are available, and we emphasize general features of the energetics of the catalytic cycles in enzymes of the DMSO reductase family.