Effect of potassium ion on the phosphorus-31 nuclear magnetic resonance spectrum of the pyridoxal 5'-phosphate cofactor of Escherichia coli D-serine dehydratase.
Effect of potassium ion on the phosphorus-31 nuclear magnetic resonance spectrum of the pyridoxal 5'-phosphate cofactor of Escherichia coli D-serine dehydratase.
复制标题
钾离子对大肠杆菌 D-丝氨酸脱水酶吡哆醛 5-磷酸辅因子磷 31 核磁共振谱的影响。
DOI：
10.1016/0003-9861(89)90565-1
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发表时间：
1989
影响因子：
3.9
通讯作者：
Shafer,JA
中科院分区：
文献类型：
--
作者：
Kojiro,CL;Marceau,M;Shafer,JA
31P NMR研究确定了钾离子如何增加大肠杆菌丝氨酸脱水酶的辅助因子亲和力。丝氨酸脱水酶是一种模型吡哆醛5 ' -磷酸酶，可将生长抑制剂-丝氨酸转化为丙酮酸和氨。在4.0 ppm （pH 7.8, 25°C）时，钾离子促进了第二次上移协因子31p共振的出现，在没有K+的情况下，在4.4 ppm处观察到的共振面积增加。Na+拮抗K+促进了第二次共振的出现。这些观察结果表明，K+和Na+稳定的构象状态不同于OPO键角、构象和/或磷酸基团的氢键。两种共振的相对强度对K+浓度的依赖性分析得出K+从丝氨酸脱水酶解离的平衡常数约为10毫米。两个共振的化学位移差表明，在pH 7.8, 25°C下，K+稳定和Na+稳定形式的酶以小于16 s−1的频率相互转换。
31P NMR studies were undertaken to determine how potassium ion increases the cofactor affinity ofEscherichia colid-serine dehydratase, a model pyridoxal 5′-phosphate requiring enzyme that converts the growth inhibitord-serine to pyruvate and ammonia. Potassium ion was shown to promote the appearance of a second upfield shifted cofactor31P resonance at 4.0 ppm (pH 7.8, 25 °C), that increased in area at the expense of the resonance at 4.4 ppm observed in the absence of K+. Na+antagonized the K+promoted appearance of the second resonance. These observations suggest that K+and Na+stabilize conformational states that differ with respect to OPO bond angle, conformation, and/or hydrogen bonding of the phosphate group. An analysis of the dependence of the relative intensities of the two resonances on the K+concentration yielded a value of ca. 10 mmfor the equilibrium constant for dissociation of K+fromd-serine dehydratase. The chemical shift difference between the two resonances indicated that the K+-stabilized and Na+-stabilized forms of the enzyme interconvert at a frequency less than 16 s−1at pH 7.8, 25 °C.