Functional consequences of the direct transfer of metabolites in muscle glycolysis.
Functional consequences of the direct transfer of metabolites in muscle glycolysis.
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肌肉糖酵解中代谢物直接转移的功能后果。
DOI：
10.1042/bst0150977
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发表时间：
1987
影响因子：
3.9
通讯作者：
Srivastava,DK
中科院分区：
文献类型：
--
作者：
Bernhard,SA;Srivastava,DK
代谢物从一种糖酵解酶（E1）转移到另一种糖酵解酶（E2），而无需预先解离到水环境中，现已证明了多种酶对。在每种情况下，E2催化的EIM 1利用率遵循对El-Ml浓度的双曲线（Michaelian）依赖性，表明代谢物（MI）通过形成El-Ez复合物转移。在E1和E之间的直接传输机制的每个示例中，我们已经发现，这两种酶依赖于连接状态以至少两种不同的构象存在;化学转化ES+ EP通常与构象互变偶联。有证据表明，E，承认El MI，而E2 M，承认E，。体内糖酵解酶的浓度通常超过其亲和底物配体的浓度。因此，在肌肉中可能建立起一个酶-酶相互作用的代谢物转移动力学系统.有证据表明，在E，E2复合体中，MI在E1和E2之间的分布几乎相等。当ES和EP具有相等的自由能时，直接转移过程得到最佳促进，这与观察结果一致，但与Albery & Knowles的理论不一致[12]。现有的热力学数据表明，相当大一部分的糖酵解的势能是存储在糖酵解酶底物复合物的形式，而不是消耗的糖转化为乳酸的总转换。有人提出，丙酮酸或乳酸的利用调节通过糖酵解在体内的流量。
The transfer of metabolite from one glycolytic enzyme (E,) to another (E,) without prior dissociation into the aqueous environment has now been demonstrated for a variety of enzyme pairs. In every case, the rate of E2-catalysed utilization of EIMl follows a hyperbolic (Michaelian) dependence on the El-Ml concentration, indicating the transfer of metabolite (MI) via the formation of an El-Ez complex. In every example of the direct transfer mechanism between El and E,. we have uncovered that both enzymes exist in at least two distinct conformations dependent on the state of ligation; the chemical transformation ES+ EP is usually coupled to the conformational interconversion. Evidence is presented that E, recognizes El MI whereas E2M, recognizes E,. The concentration of glycolytic enzymes in vivo usually exceeds the concentration of their affine substrate ligands. Thus a dynamic system of metabolite transfer via enzymeenzyme interaction may be set up in muscle. Evidence is presented indicating that the distribution of MI between El and E2 in the E, E2 complex is nearly equal. The direct transfer process is optimally facilitated when ES and EP are of equal free energy, consistent with the observations but not the theory of Albery & Knowles [12]. Available thermodynamic data indicate that a substantial fraction of the potential energy of glycolysis is stored in the form of glycolytic enzyme substrate complexes rather than dissipated by the total conversion of sugar to lactate. It is proposed that the utilization of pyruvate or lactate regulates the flux through glycolysis in vivo.