Formation and decomposition of a phosphorylated intermediate in the reaction of Na+-K+ dependent ATPase
Formation and decomposition of a phosphorylated intermediate in the reaction of Na+-K+ dependent ATPase
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Na-K 依赖性 ATP 酶反应中磷酸化中间体的形成和分解
DOI：
10.1093/oxfordjournals.jbchem.a129297
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发表时间：
1970
影响因子：
2.7
通讯作者：
Y. Tonomura
中科院分区：
文献类型：
--
作者：
T. Kanazawa;M. Saito;Y. Tonomura
1.在反应介质中加入过量的EDTA使磷酸化反应停止时，磷酸化蛋白浓度[EP]随时间呈指数下降。Ep下降的一级速率常数kd随KCl浓度的增加而增加(在0.6 mM KCl时分别为0.50和2.26秒~(-1))，且与氯化钠和三磷酸腺苷的浓度无关。加入过量的未标记三磷酸腺苷后，E32P降低的速率常数kd与加入EDTA2后观察到的速率常数基本相同。稳态时，ATP水解率与EP浓度之比vo/[Ep]随KCl浓度的增加而显著增加(分别为0.57秒和4.43秒-1)，但不受ATP浓度的影响。一般而言，这一比率vo/[ep]不同于kd。在无KCl的情况下，它几乎等于k，1，但随着KCl浓度的增加，其增加的速度比Ka快。在0.6 Met KCl存在下，为2倍ka。
1. When the phosphorylation reaction was stopped by adding excess EDTA to the reaction medium, the concentration of phosphorylated protein,[EP], decreased exponentially with time. The first-order rate constant of the decrease in EP, kd, increased with increase in KCl concentration (0.50 and 2.26 sec-1, respectively, in the absence and presence of 0.6 mm KCl), and was independent of the concentrations of NaCl and ATP. The rate constant, kd, of the decrease in E32P after the addition of excess unlabelled ATP was essentially the same as that observed after the addition of EDTA.2. The ratio of the rate of ATP hydrolysis to the EP concentration in the steady state, vo/[EP], increased markedly with increase in KCl concentration (0.57 and 4.43 sec-1, respectively, in the absence and presence of 0.6 mm KCl), but was unaffected by changing the ATP concentration. In general, the ratio, vo/[EP], differed from kd. It was nearly equal to k, 1 in the absence of KCl, but it increased more rapidly than ka with increase in the KCl concentration. In the presence of 0.6 met KCl, it was twice ka.