Ivane Beritashvili Center of Experimental Biomedicine, 14 Gotua Str., 0160, Tbilisi, Georgia.
Cell Biochem Biophys. 2022 Mar;80(1):23-29. doi: 10.1007/s12013-021-01032-6. Epub 2021 Aug 26.
A comparative kinetic analysis of albino rat brain synaptic and kidney plasma membrane fraction Na,K-ATPase was performed to comprehend the different levels of sensitivity of these fractions to the neurotransmitter noradrenaline. Noradrenaline (NA) inhibits the rat brain synaptic membrane Na,K-ATPase, changes the stoichiometry of Na and K and shifts the enzyme system from an MgATP to an Mg dependent cycle. While the kidney plasma membrane fraction Na,K-ATPase is not sensitive to noradrenaline. To investigate the mechanism underlying this difference, we studied enzyme velocity dependence on the concentration of Mg. The 1/V = f(Mg) function has shown different kinetic features for the synaptic and kidney plasma membrane Na,K-ATPase. With the addition of ethylene glycol tetraacetic acid (EGTA) to the reaction medium the geometric form of 1/V = f(Mg) function is affected differently. We thereafter measured the essential activator number for Na and K with, in excess Mg. The results of these experiments reveal that, contrary to the synaptic membrane Na,K-ATPase, the kidney plasma membrane fraction Na,K-ATPase does not possess an Mg dependent cycle and noradrenaline exhibits different modulatory effects on the enzyme system.
为了理解这些部分对神经递质去甲肾上腺素的不同敏感程度，我们对白化大鼠脑组织突触和肾脏质膜部分 Na，K-ATP 酶进行了比较动力学分析。去甲肾上腺素（NA）抑制大鼠脑组织突触质膜 Na，K-ATP 酶，改变 Na 和 K 的比例，并将酶系统从 MgATP 依赖性循环转变为 Mg 依赖性循环。而肾脏质膜部分 Na，K-ATP 酶对去甲肾上腺素不敏感。为了研究这种差异的机制，我们研究了酶对 Mg 浓度的速度依赖性。1/V=f（Mg）函数显示了突触和肾脏质膜 Na，K-ATP 酶的不同动力学特征。在反应介质中加入乙二胺四乙酸（EGTA）后，1/V=f（Mg）函数的几何形状受到不同的影响。此后，我们在过量 Mg 存在下测量了 Na 和 K 的必需激活数。这些实验的结果表明，与突触质膜 Na，K-ATP 酶相反，肾脏质膜部分 Na，K-ATP 酶不具有 Mg 依赖性循环，去甲肾上腺素对酶系统表现出不同的调节作用。
