Functional energetic landscape in the allosteric regulation of muscle pyruvate kinase. 1. Calorimetric study.
Functional energetic landscape in the allosteric regulation of muscle pyruvate kinase. 1. Calorimetric study.
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DOI：
10.1021/bi900279x
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发表时间：
2009-10-13
期刊：
影响因子：
2.9
通讯作者：
Lee, J. Ching
中科院分区：
文献类型：
--
作者：
Herman, Petr;Lee, J. Ching
兔肌丙酮酸激酶（RMPK）是糖酵解途径中一种重要的变构酶，可催化磷酸烯醇丙酮酸（PEP）向ADP的转移。在4 ~ 45℃的温度范围内，用等温滴定量热法（ITC）表征了RMPK变构调控机制的能量格局。对RMPK与底物PEP和ADP结合的ITC数据、与变构抑制剂Phe结合的ITC数据以及与ADP和Phe结合的ITC数据进行全局分析。提取了表征链接-多平衡系统的热力学参数。他们发现了四个新颖的见解。ADP对T态或r态的结合偏好与温度有关；即在高温和低温下分别更有利于T态和r态。这种对R态和t态亲和力的交叉表明ADP在调节RMPK的变构行为中起着复杂的作用。根据温度的不同，ADP的结合可以调节RMPK的活性，使酶处于R或t状态。2. Phe与ADP的结合呈负偶联，即Phe和ADP不倾向于与RMPK的同一亚基结合。3. 与各种平衡相联系的质子的释放或吸收是特定于特定反应的。因此，pH会对这些连锁平衡产生复杂的影响，导致质子成为RMPK的变构调节配体。4. R↔T平衡伴随着一个显著的ΔCp，使得RMPK在生理条件下对温度最敏感。在肌肉活动期间，pH值和温度都会发生波动；因此，本研究结果具有生理学意义。
Rabbit muscle pyruvate kinase (RMPK) is an important allosteric enzyme of the glycolytic pathway catalyzing a transfer of the phosphate from phosphoenolpyruvate (PEP) to ADP. The energetic landscape of the allosteric regulatory mechanism of RMPK was characterized by isothermal titration calorimetry (ITC) in the temperature range from 4°C to 45°C. ITC data for RMPK binding to substrates PEP and ADP, for the allosteric inhibitor Phe, as well as for combination of ADP and Phe were globally analyzed. The thermodynamic parameters characterizing the linked-multiple- equilibria system were extracted. Four novel insights were uncovered 1. The binding preference of ADP for either the T- or R-state is temperature dependent; namely, more favorably to the T- and R-state at high and low temperature, respectively. This cross over of affinity towards R and T-state implies that ADP plays a complex role in modulating the allosteric behavior of RMPK. Depending on the temperature, binding of ADP can regulate RMPK activity by favoring the enzyme to either the R- or T-state. 2. The binding of Phe is negatively coupled to that of ADP i.e. Phe and ADP prefer not to bind to the same subunit of RMPK. 3. The release or absorption of protons linked to the various equilibria is specific to the particular reaction. As a consequence, pH will exert a complex effect on these linked equilibria resulting in proton being an allosteric regulatory ligand of RMPK. 4. The R↔T equilibrium is accompanied by a significant ΔCp rendering RMPK most sensitive to temperature under physiological conditions. During muscle activity, both pH and temperature fluctuations are known to happen; thus, results of this study are physiologically relevant.
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影响因子：
2.9
作者：
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通讯作者：
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影响因子：
3.4
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影响因子：
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通讯作者：
MACFARLANE, N
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作者：
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通讯作者：
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