大肠杆菌B中精氨酰-tRNA合成酶的研究。金属在酶催化中的双重作用。
Studies on arginyl-tRNA synthetase from Escherichia coli B. Dual role of metals in enzyme catalysis.
作者信息
Craine J E, Peterkofsky A
出版信息
J Biol Chem. 1976 Jan 10;251(1):241-6.
Studies carried out in arginyl-tRNA synthetase from Escherichia coli indicate that metals may have two functional roles in the catalytic mechanism. Complete metal activation is observed when MgCl2, MnCl2, CoCl2, or FeCl2 is present at a concentration (5.0 mM) in excess of the total ATP concentration (2.0 mM). When CaCl2 is substituted for MgCl2, activity is not observed unless a small amount (0.1 mM) of MgCl2, MnCl2, CoCl2, FeCl2, or ZnCl2 (unable to produce activity alone at 5.0 mM) is added. A model, based on kinetic data, is proposed in which the enzyme possesses a site for free metal, which, when filled, lowers the Km for all three substrates (arginine, tRNAArg, and metal-ATP) and increases the Vmax of the reaction.
对来自大肠杆菌的精氨酰 - tRNA合成酶进行的研究表明，金属在催化机制中可能具有两种功能作用。当MgCl₂、MnCl₂、CoCl₂或FeCl₂以超过总ATP浓度（2.0 mM）的浓度（5.0 mM）存在时，可观察到完全的金属激活。当用CaCl₂替代MgCl₂时，除非添加少量（0.1 mM）的MgCl₂、MnCl₂、CoCl₂、FeCl₂或ZnCl₂（在5.0 mM时单独不能产生活性），否则观察不到活性。基于动力学数据提出了一个模型，其中该酶具有一个游离金属位点，当该位点被占据时，会降低所有三种底物（精氨酸、tRNAArg和金属 - ATP）的Km，并增加反应的Vmax。
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