Department of Biology, Faculty of Science, University of Shahrekord, Shahrekord, P.O. Box 115, Iran.
Department of Biology, Faculty of Science, University of Shahrekord, Shahrekord, P.O. Box 115, Iran.
Int J Biol Macromol. 2020 May 15;151:1250-1258. doi: 10.1016/j.ijbiomac.2019.10.171. Epub 2019 Nov 22.
Osmolytes such as sucrose can interact with the proteins. The aim of the present investigation was to characterize how sucrose could affect the structure, thermal stability and the kinetic of proteinase K. UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular docking, molecular dynamic simulation studies were used to this end. The UV-vis results are represented the intensity enhancement 270 nm due to alteration in the local environment of Tyr and Trp amino acid residues illustrated the tertiary structure changes of proteinase K. The intrinsic fluorescence intensity was decreased regularly with increase the ligand concentration. The secondary structure alterations were revealed an increase in the α-helix content of enzyme. The activity of enzyme was increased in the presence of sucrose. Thus, sucrose is an activator for proteinase K. Molecular docking results show a negative value for the Gibbs free energy of the binding confirming the spontaneous proteinase K-sucrose complexation and in agreement with fluorescence results. On the other hand, the thermal stability of proteinase K was investigated in the presence of sucrose. The obtained results show that sucrose led to increment the stability of enzyme in a concentration dependent manner. These results are confirmed by the molecular dynamic simulation technique.
渗透剂（如蔗糖）可以与蛋白质相互作用。本研究的目的是描述蔗糖如何影响蛋白酶 K 的结构、热稳定性和动力学。为此，我们使用了紫外-可见光谱、荧光光谱、圆二色性、分子对接和分子动力学模拟研究。紫外-可见结果表明，由于 Tyr 和 Trp 氨基酸残基的局部环境发生变化，270nm 处的强度增强表明了蛋白酶 K 的三级结构发生了变化。随着配体浓度的增加，内源荧光强度呈规则下降。二级结构的变化表明酶的α-螺旋含量增加。在蔗糖存在下，酶的活性增加。因此，蔗糖是蛋白酶 K 的激活剂。分子对接结果显示结合的吉布斯自由能为负值，证实了蛋白酶 K-蔗糖复合物的自发形成，与荧光结果一致。另一方面，在蔗糖存在下研究了蛋白酶 K 的热稳定性。结果表明，蔗糖以浓度依赖的方式导致酶稳定性增加。这些结果得到了分子动力学模拟技术的证实。
