Branched reaction mechanism for the Na/K pump as an alternative explanation for a nonmonotonic current vs. membrane potential response.
Branched reaction mechanism for the Na/K pump as an alternative explanation for a nonmonotonic current vs. membrane potential response.
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Na/K 泵的分支反应机制作为非单调电流与膜电位响应的替代解释。
DOI：
10.1007/bf01868538
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Milanick,MA
中科院分区：
文献类型：
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作者：
Milanick,MA
非单调的速度-膜电位曲线常被认为是电荷在电场中运动的两个步骤的证据。然而，一个分支的反应计划，其中只有一个步骤涉及电荷移动每个周期可能会导致非单调响应。在酶动力学中也有类似的情况：非单调的速度-底物曲线常被认为是两个不同底物结合位点的证据。然而，其中每个完整循环仅一种底物结合的分支反应方案可导致非单调响应（参见Segel，I. H. 1975.酶动力学pp. 657-659. John Wiley & Sons，纽约）。一些分析约束的支化反应机制，引起非单调响应的速率常数的相对大小的推导。有两个必要条件。(i)分支路径中至少一个步骤的速率必须小于分支之后步骤的速率。(ii)S首先结合的途径的速率必须比另一途径的速率慢。类似的情况下，产生非单调的电流与膜电位曲线。Na/K泵的分支机制为非单调泵电流与膜电位的关系提供了另一种解释。
Nonmonotonic velocityvs.membrane potential curves are often taken as evidence that two steps involve charge movement through the electric field. However, a branched reaction scheme in which only one step involves charge movement per cycle can lead to a nonmonotonic response. A similar case occurs in enzyme kinetics: nonmonotonic velocityvs.substrate curves are often taken as evidence for two different substratebinding sites. However, a branched reaction scheme in which only one substrate binds per complete cycle can lead to a nonmonotonic response (seeSegel, I.H. 1975. Enzyme Kinetics. pp. 657–659. John Wiley & Sons, New York). Some analytical constraints on the relative sizes of the rate constants of a branched reaction mechanism that give rise to nonmonotonic responses are derived. There are two necessary conditions. (i) The rate of at least one step in the branched pathway must be less than the rate of the step after the branch. (ii) The rate of the pathway in which S binds first must be slower than the rate of the other pathway. Analogous cases give rise to nonmonotonic currentvs.membrane potential curves. A branched mechanism for the Na/K pump provides an alternative explanation for a nonmonotonic pump currentvs.membrane potential relationship.