Urayama O, Nakao M
J Biochem. 1979 Nov;86(5):1371-81. doi: 10.1093/oxfordjournals.jbchem.a132654.
We compared several Na,K-ATPase preparations from various organs of the rat. The brain Na,K-ATPase differed from the enzymes of other organs in its pH dependence and responses to ouabain and N-ethylmaleimide in spite of similarities in the kinetic parameters of activation by Na+, K+, Mg2+, and ATP. The optimum pH of the brain MaI-enzyme was at 7.4 to 7.5 at 37 degrees D. The Lubrol extract of this brain enzyme preparation showed a lower optimum oH of 6.6. When the Lubrol extract of the brain was fractionated wtih (NH4)2SO4, the activity of the precipitate in the neutral pH region was restored. On the other hand, the optimum pH of the kidney NaI-enzyme was slightly affected by Lubrol and ammonium sulfate treatments (pH 7.5 leads to 7.3). The brain enzyme (K 1/2 = 0.9 microM) showed about 100-fold higher sensitivity to ouabain than the enzymes from other organs (I 1/2 = 100 microM) in the presence of 120 mM Na+ and 10 mM K+. In a Hill plot of the ouabain inhibition, the former failed to give a linear relationship, while the latter gave a straight line with a Hill coefficient of 1.0. The effect of K4 on the brain enzyme-ouabain interaction led us to consider that the brain enzyme might have two components as regards ouabain affinity, high and low affinity components. The time course of N-ethylmaleimide inhibition of the brain enzyme was rapid and biphasic, while the kidney enzyme showed only a slow phase following pseudo-first order kinetics. ATP protected the kidney enzyme activity completely agai,st N-ethylmaleimide inhibition, but the protection of the brain enzyme activity by ATP was only partial. We divided rat Na,K-ATPases into two groups, the brain type, which is restricted to the central nervous system, and the kidney type, which is found in most organs.
我们比较了从大鼠不同器官获取的几种钠钾 - ATP酶制剂。尽管在由Na⁺、K⁺、Mg²⁺和ATP激活的动力学参数方面存在相似性，但脑钠钾 - ATP酶在其pH依赖性以及对哇巴因和N - 乙基马来酰亚胺的反应方面与其他器官的酶不同。在37摄氏度时，脑MaI - 酶的最适pH为7.4至7.5。这种脑酶制剂的 Lubrol提取物显示出较低的最适pH，为6.6。当用脑的Lubrol提取物用硫酸铵分级分离时，沉淀物在中性pH区域的活性得以恢复。另一方面，肾NaI - 酶的最适pH受到Lubrol和硫酸铵处理的轻微影响（从pH 7.5变为7.3）。在存在120 mM Na⁺和10 mM K⁺的情况下，脑酶（K₁/₂ = 0.9 μM）对哇巴因的敏感性比其他器官的酶（I₁/₂ = 100 μM）高约100倍。在哇巴因抑制的希尔图中，前者未呈现线性关系，而后者给出了斜率为1.0的直线。K⁴对脑酶 - 哇巴因相互作用的影响使我们认为，就哇巴因亲和力而言，脑酶可能有两个组分，即高亲和力组分和低亲和力组分。N - 乙基马来酰亚胺对脑酶的抑制时间进程迅速且呈双相性，而肾酶仅呈现遵循假一级动力学的缓慢相。ATP可完全保护肾酶活性免受N - 乙基马来酰亚胺的抑制，但ATP对脑酶活性的保护只是部分的。我们将大鼠钠钾 - ATP酶分为两组，即仅限于中枢神经系统的脑型和存在于大多数器官中的肾型。
