Functional energetic landscape in the allosteric regulation of muscle pyruvate kinase. 3. Mechanism.
Functional energetic landscape in the allosteric regulation of muscle pyruvate kinase. 3. Mechanism.
复制标题
肌肉丙酮酸激酶变构调节中的功能性能量景观。
DOI：
10.1021/bi900281s
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发表时间：
2009
期刊：
影响因子：
2.9
通讯作者：
Lee,JChing
中科院分区：
文献类型：
--
作者：
Herman,Petr;Lee,JChing
哺乳动物丙酮酸激酶以四种亚型存在，其特征根据不同组织的特定代谢要求进行调整。所有的异构体，除了肌肉异构体，表现出典型的变构行为。肌肉同种型的情况是一个谜。它被别构抑制剂Phe抑制，但传统上不被认为是别构酶。在这一系列研究中，建立了兔肌肉丙酮酸激酶（RMPK）的充满活力的景观。Phe的抑制现象是生理性的。此外，热力学的温度波动和伴随的pH值变化的肌肉活动的结果进行了阐述。我们已经证明：（1）在各种关联反应中释放或吸收的质子数的差异增加了另一个控制水平，以改变结合常数和活性态与非活性态的平衡变化（后者定量地控制RMPK的活性）;（2）在生理温度下，ADP在RMPK的变构机制中起主要作用（取决于温度，ADP可以通过优先结合无活性形式和底物而承担作为抑制剂的双重和相反的作用）;以及（3）对生理条件下RMPK行为的模拟表明，参与调节的21个热力学参数的净结果是良好的，调节以允许酶对温度和配体浓度的即使微小变化的最大响应。
Mammalian pyruvate kinase exists in four isoforms with characteristics tuned to specific metabolic requirements of different tissues. All of the isoforms, except the muscle isoform, exhibit typical allosteric behavior. The case of the muscle isoform is a conundrum. It is inhibited by an allosteric inhibitor, Phe, yet it has traditionally not been considered as an allosteric enzyme. In this series of study, an energetic landscape of rabbit muscle pyruvate kinase (RMPK) was established. The phenomenon of inhibition by Phe is shown to be physiological. Furthermore, the thermodynamics for the temperature fluctuation and concomitant pH change as a consequence of muscle activity were elucidated. We have shown that (1) the differential number of protons released or absorbed with regard to the various linked reactions adds another level of control to shift the binding constants and equilibrium of active ⇆ inactive state changes (the latter controls quantitatively the activity of RMPK); (2) ADP plays a major role in the allosteric mechanism in RMPK under physiological temperatures (depending on the temperature, ADP can assume dual and opposite roles of being an inhibitor by binding preferentially to the inactive form and a substrate); and (3) simulation of the RMPK behavior under physiological conditions shows that the net results of the 21 thermodynamic parameters involved in the regulation are well-tuned to allow the maximal response of the enzyme to even minute changes in temperature and ligand concentration.