Willson V J, Tipton K F
Eur J Biochem. 1981 Jan;113(3):477-83. doi: 10.1111/j.1432-1033.1981.tb05088.x.
Two independent methods were used to assess the dependence of the activity of ox brain NAD+-dependent isocitrate dehydrogenase on the concentration of magnesium ions. The results indicated the complex between magnesium and isocitrate to be the true substrate for the enzyme. Free isocitrate is neither a substrate nor an inhibitor of the enzyme but free magnesium ions inhibit competitively with respect to the magnesium-isocitrate complex. The inhibition of the enzyme by ATP and citrate appears to be largely explicable in terms of their effects on the concentration of the complex between Mg2+ and isocitrate. The dependence of the activation of the enzyme by ADP on the concentration of magnesium ions suggests that free ADP, rather than its complex with Mg2+, is the activator.
采用两种独立的方法来评估牛脑NAD⁺依赖性异柠檬酸脱氢酶的活性对镁离子浓度的依赖性。结果表明，镁与异柠檬酸之间的复合物是该酶的真正底物。游离异柠檬酸既不是该酶的底物也不是抑制剂，但游离镁离子相对于镁 - 异柠檬酸复合物具有竞争性抑制作用。ATP和柠檬酸盐对该酶的抑制作用似乎在很大程度上可以用它们对Mg²⁺与异柠檬酸之间复合物浓度的影响来解释。ADP对该酶的激活作用对镁离子浓度的依赖性表明，游离ADP而非其与Mg²⁺的复合物是激活剂。
