Ali L Z, Sloan D L
J Inorg Biochem. 1986 Dec;28(4):407-15. doi: 10.1016/0162-0134(86)80026-5.
We have observed previously that the reactions catalyzed by hypoxanthine/guanine phosphoribosyltransferase (HGPRTase) are activated by Mg(II), Mn(II), and Co(II), and we have defined the mechanism by which these activations proceed [Biochemistry 22, 3419-3424 (1983)]. A more extensive survey of the kinds of metal ions that will activate the HGPRTase catalysis now has been completed through the use of an HPLC assay procedure. Although Fe(II) and Ca(II) are unable to activate this reaction, a significant activation was achieved with the addition of spectroscopically pure Zn(II) to the assay solution. In addition some IMP synthesis resulted from the addition of Ni(II) to the assay mixture. Both the Zn(II) and Ni(II) kinetic effects on HGPRTase over a limited metal ion concentration range have been analyzed through the use of curve-fitting exercises. These results, in addition to the similar pH profiles for the activations by Mg(II), Mn(II), Co(II), and Zn(II), suggest that all of these metal ions activate the HGPRTase-catalyzed synthesis of IMP by way of the same mechanism [model II as defined by London and Steck, Biochemistry 8, 1767-1779 (1969)], during which two divalent ions bind to the HGPRTase active site per molecule of PRibPP.
我们之前观察到，次黄嘌呤/鸟嘌呤磷酸核糖转移酶（HGPRTase）催化的反应可被Mg(II)、Mn(II)和Co(II)激活，并且我们已经阐明了这些激活作用的发生机制[《生物化学》22, 3419 - 3424 (1983)]。现在，通过使用高效液相色谱（HPLC）分析方法，已经完成了对能够激活HGPRTase催化作用的各类金属离子的更广泛研究。尽管Fe(II)和Ca(II)无法激活此反应，但向分析溶液中添加光谱纯的Zn(II)可实现显著激活。此外，向分析混合物中添加Ni(II)会产生一些IMP合成。通过曲线拟合分析，研究了在有限的金属离子浓度范围内Zn(II)和Ni(II)对HGPRTase的动力学影响。这些结果，连同Mg(II)、Mn(II)、Co(II)和Zn(II)激活作用的相似pH曲线，表明所有这些金属离子通过相同的机制[如London和Steck在《生物化学》8, 1767 - 1779 (1969)中所定义的模型II]激活HGPRTase催化的IMP合成，在此过程中，每分子PRibPP有两个二价离子结合到HGPRTase活性位点。
