Phosphate inhibition of the human red cell sodium pump: simultaneous binding of adenosine triphosphate and phosphate.
Phosphate inhibition of the human red cell sodium pump: simultaneous binding of adenosine triphosphate and phosphate.
复制标题
磷酸盐抑制人红细胞钠泵：三磷酸腺苷和磷酸盐同时结合。
DOI：
10.1113/jphysiol.1988.sp017136
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Sachs,JR
中科院分区：
文献类型：
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作者：
Sachs,JR
1. 人红细胞血影的Na+泵进行的Na+-K+交换和人红细胞膜的Na+ + K+依赖性三磷酸腺苷酶（Na+,K+-ATPase）活性受到MgPO4的抑制，而不是游离磷酸盐的抑制；同样，泵进行 K+-K+ 交换的底物是 MgPO4 而不是游离磷酸盐。 2. MgPO4 对 Na+、K+-ATP 酶活性的抑制仅与 ATP 部分竞争（混合型），并且在不含 Na+ 的溶液和含有相对高浓度 ATP 的不含 K+ 的幽灵中测量的 MgPO4 对 Na+-K+ 交换的抑制与外部 K+ 部分不竞争（混合型）。 3. 当在无 K+ 鬼影和无 Na+ 溶液中进行测量时，或者在高 ATP 浓度下测量 Na+,K+-ATP 酶活性时，MgPO4 的抑制与细胞 Na+ 不具有竞争性。这一观察结果与 Na+ 泵的 Albers-Post 反应机制不一致，并表明存在另一种反应途径，其中 ATP 在磷酸盐释放之前与酶结合。 4. MgPO4 单调抑制在不含 Na+ 和 K+ 的溶液中发生的非偶联 Na+ 流出。与 Na+-K+ 交换相比，非偶联流出似乎对 MgPO4 抑制更敏感。 5.三硝基苯腺苷-5'-四磷酸在MgPO4存在下刺激K+-K+交换，TNP四磷酸腺苷的刺激特性与三硝基苯腺苷-5'-三磷酸或-5'-二磷酸的刺激特性差别不大。刺激 K+-K+ 交换的核苷酸结合位点必须能够容纳具有四个磷酸基团线性阵列的核苷酸。
1. The Na+‐K+ exchange carried out by the Na+ pump of human red cell ghosts and the Na+ + K+‐dependent adenosine triphosphatase (Na+,K+‐ATPase) activity of human red cell membranes are inhibited by MgPO4 rather than by free phosphate; similarly, the substrate for the K+‐K+ exchange carried out by the pump is MgPO4 rather than free phosphate. 2. Inhibition of the Na+, K+‐ATPase activity by MgPO4 is only partially competitive (mixed type) with ATP, and MgPO4 inhibition of the Na+‐K+ exchange measured in Na+‐free solutions and in K+‐free ghosts which contain ATP at relatively high concentration is partially uncompetitive (mixed type) with external K+. 3. When measurements were made in K+‐free ghosts and Na+‐free solutions, or when Na+,K+‐ATPase activity was measured at high ATP concentrations, inhibition by MgPO4 was non‐competitive with cell Na+. This observation is not consistent with the Albers‐Post reaction mechanism of the Na+ pump, and suggests the presence of an alternative reaction pathway in which ATP combines with the enzyme before phosphate is released. 4. MgPO4 monotonically inhibited the uncoupled Na+ efflux which occurs in solutions free of both Na+ and K+. The uncoupled efflux seemed to be more sensitive to MgPO4 inhibition than the Na+‐K+ exchange. 5. Trinitrophenyladenosine‐5'‐tetraphosphate stimulated the K+‐K+ exchange in the presence of MgPO4, and the characteristics of stimulation by TNP adenosine tetraphosphate were little different from the characteristics of stimulation by trinitrophenyladenosine‐5'‐triphosphate or ‐5'‐diphosphate. The nucleotide binding site at which K+‐K+ exchange is stimulated must be able to accommodate a nucleotide with a linear array of four phosphate groups.