Kwan C Y, Erhard K, Davis R C
J Biol Chem. 1975 Aug 10;250(15):5951-9.
Stoichiometry, kinetics, and optical properties of rabbit muscle pyruvate kinase activated with Co(II), Ni(II), Mg(II), and Mn(II) were studied. The stoichiometry of metal binding to enzyme was found to be 4 metal ions per tetrameric enzyme for Co(II) and Ni(II) by carrying out circular dichroic titrations. Cu(II) and Fe(II) were inactive. Ca(II) and Zn(II) were not activating, and were inhibitory with respect to all of the active cations. The temperature dependence of the optimal velocity is similar for all activating metals. The pH rate profiles suggest that there are two classes of enzyme activation by metal ions. Mg(II) and Mn(II) are quite similar to each other while Co(II) and Ni(II) are different from them but similar to each other. Absorption, natural, and magnetic CD in the visible region were used to probe the environment of the activating divalent cation in Ni(II)- and Co(II)-activated pyruvate kinase and their complexes with substrates and inhibitors...
研究了用Co(II)、Ni(II)、Mg(II)和Mn(II)激活的兔肌肉丙酮酸激酶的化学计量学、动力学和光学性质。通过进行圆二色滴定，发现对于Co(II)和Ni(II)，金属与酶结合的化学计量为每个四聚体酶结合4个金属离子。Cu(II)和Fe(II)无活性。Ca(II)和Zn(II)没有激活作用，并且对所有活性阳离子都有抑制作用。所有激活金属的最佳速度的温度依赖性相似。pH速率曲线表明金属离子对酶有两类激活作用。Mg(II)和Mn(II)彼此非常相似，而Co(II)和Ni(II)与它们不同，但彼此相似。利用可见区域的吸收光谱、自然CD光谱和磁CD光谱来探测Ni(II)和Co(II)激活的丙酮酸激酶中激活二价阳离子的环境及其与底物和抑制剂的复合物……
