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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Thermodynamic analysis of Kex2 activity: The acylation and deacylation steps are potassium- and substrate-dependent
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Thermodynamic analysis of Kex2 activity: The acylation and deacylation steps are potassium- and substrate-dependent

机译：kex2活性的热力学分析：酰化和脱酰化步骤是钾和基底依赖性的

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摘要

Kex2 is the prototype of a large family of eukaryotic subtilisin-related proprotein-processing proteases that cleave at sites containing pairs of basic residues. Here, we studied the effects of KCl on the individual rate constants of association, dissociation, acylation and deacylation and determined the thermodynamic parameters at each step of the Kex2 reaction. Potassium bound Kex2 with K-D = 20.3 mM. The order in which potassium entered the reaction system modified the effect of activation or inhibition, which depended on the size of the substrate. A possible allosteric potassium binding site at the S-6 subsite was involved in activation, and a distant site located between the catalytic domain and the P-domain was involved in inhibition. Potassium decreased the energetic barriers of almost all steps of catalysis. The acylation of Ac-PMYKR-AMC in the absence of potassium was the rate-limiting step. Therefore, for substrates containing a P-1-Arg, the deacylation step is not necessarily the rate-limiting event, and other residues at the P' positions may participate in controlling the acylation and deacylation steps. Thus, it is reasonable to conclude that potassium is involved in the processing of the alpha-mating factor that promotes Ca2+, mobilization by activating a high-affinity Ca2+-influx system to increase the cytosolic [Ca2+], resulting in the activation of channels that are essential for the survival of Saccharomyces cerevisine cells.
机译：Kex2是大型真核枯草杆菌蛋白相关的ProProtein-加工蛋白酶的原型，可在含有成对的基本残基的位点上切割。在这里，我们研究了KCl对关联，解离，酰化和脱酰化的个体速率常数的影响，并确定了KEX2反应的每个步骤中的热力学参数。钾结合的Kex2，K-D = 20.3毫米。钾进入反应体系的顺序改性了激活或抑制的效果，这取决于基材的尺寸。 S-6套房的可能的颠覆钾结合位点涉及活化，并且位于催化结构域和P域之间的远处抑制。钾降低了几乎所有催化步骤的能量障碍。在没有钾没有钾的AC-PMYKR-AMC的酰化是速率限制步骤。因此，对于含有P-1-Arg的底物，脱酰化步骤不一定是速率限制事件，P'位置处的其他残基可以参与控制酰化和脱酰化步骤。因此，结论是合理的，结论钾涉及促进Ca2 +的α交配因子的加工，通过激活高亲和力Ca2 + -Influx系统来增加胞质溶胶[Ca2 +]，导致通道的激活对酿酒酵母细胞的存活至关重要。

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