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首页> 外文期刊>Biochemistry >Effect of Protein Dynamics upon Reactions that Occur in the Heme Pocket of Horseradish Peroxidase.
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Effect of Protein Dynamics upon Reactions that Occur in the Heme Pocket of Horseradish Peroxidase.

机译：蛋白质动力学对辣根过氧化物酶血红素口袋中发生的反应的影响。

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摘要

Free base and Pd porphyrin derivatives of horseradish peroxidase show long-lived excited states that are quenched by the presence of the peroxidase inhibitor, benzhydroxamic acid. The relaxation times of the excited-state luminescence and the rates of the quenching reaction for these derivatives of peroxidase were monitored as a function of pH, temperature, and viscosity with the view of examining how protein dynamics affect the quenching reaction. As solvent viscosity increases, the rate decreases, but at the limit of very high viscosity (i.e., high glycerol or sugar glass) the quenching still occurs. A model is presented that is consistent with the known structure of the enzyme-inhibitor complex. It is considered that the inhibitor is held at an established position but that solvent-dependent and independent motions allow a limited diffusion of the two reactants. Since there is a steep dependence upon distance and orientation, the diffusion toward the favorable position for reaction enhances the reaction rate. The solvent viscosity dependent and independent effects were separated and analyzed. The importance of internal reaction dynamics is demonstrated in the observation that rigidity of solvent imposed by incorporating the protein into glass at room temperature allows the reaction to occur, while the reaction is inhibited at low temperature. The results emphasize that protein dynamics plays a role in determining reaction rates.
机译：辣根过氧化物酶的游离碱和Pd卟啉衍生物表现出长寿命的激发态，该态被过氧化物酶抑制剂苯氧肟酸的存在淬灭。这些过氧化物酶衍生物的激发态发光的弛豫时间和淬灭反应的速率作为pH，温度和粘度的函数进行监测，以检查蛋白质动力学如何影响淬灭反应。随着溶剂粘度的增加，速率降低，但是在非常高的粘度（即高甘油或糖玻璃）的极限下，仍然发生淬灭。提出了与酶-抑制剂复合物的已知结构一致的模型。认为抑制剂被保持在确定的位置，但是溶剂依赖性和独立运动允许两种反应物的有限扩散。由于高度依赖于距离和取向，因此朝着反应的有利位置的扩散提高了反应速率。分离并分析了溶剂粘度依赖性和非依赖性效应。内部反应动力学的重要性在以下观察中得到了证明：通过在室温下将蛋白质掺入玻璃中而施加的溶剂的刚性允许反应发生，而在低温下则抑制了反应。结果强调，蛋白质动力学在确定反应速率中起作用。

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