Functional characterization of a novel ArgA from Mycobacterium tuberculosis
Functional characterization of a novel ArgA from Mycobacterium tuberculosis
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DOI：
10.1128/jb.187.9.3039-3044.2005
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发表时间：
2005-05-01
影响因子：
3.2
通讯作者：
Blanchard, JS
中科院分区：
文献类型：
--
作者：
Errey, JC;Blanchard, JS
结核分枝杆菌基因Rv 2747编码一种新的19-kDa ArgA，其催化L-精氨酸生物合成的起始步骤，即L-谷氨酸转化为α-N-乙酰基-L-谷氨酸。初速度研究表明，Rv 2747通过一个顺序的动力学机制，与K值为280 mM的L-谷氨酰胺和150 μ M的乙酰辅酶A和与k（猫）值为200分钟（-1）。用L-谷氨酸盐的初始速度研究表明，即使在600 mM的浓度下，也没有观察到饱和。因此，只能计算出125 M-1 min（-1）的k（cat）/K-m值。抑制研究表明，该酶是强烈调节的L-精氨酸，最终产品的途径（50%抑制浓度，26 μ M）。该酶被完全抑制500 μ M精氨酸，希尔系数为0.60，表明负合作的L-精氨酸的结合。
The Mycobacterium tuberculosis gene Rv2747 encodes a novel 19-kDa ArgA that catalyzes the initial step in L-arginine biosynthesis, namely the conversion Of L-glutamate to alpha-N-acetyl-L-glutamate. Initial velocity studies reveal that Rv2747 proceeds through a sequential kinetic mechanism, with K values of 280 mM for L-glutamine and 150 mu M for acetyl-coenzyme A and with a k(cat) value of 200 min(-1). Initial velocity studies with L-glutamate showed that even at concentrations of 600 mM, saturation was not observed. Therefore, only a k(cat)/K-m value of 125 M-1 min(-1) can be calculated. Inhibition studies reveal that the enzyme is strongly regulated by L-arginine, the end product of the pathway (50% inhibitory concentration, 26 mu M). The enzyme was completely inhibited by 500 mu M arginine, with a Hill coefficient of 0.60, indicating negatively cooperative binding of L-arginine.