Vidya Jalaja, Ushasree Mrudula Vasudevan, Pandey Ashok
Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum 695 019, India.
Enzyme Microb Technol. 2014 Mar 5;56:15-9. doi: 10.1016/j.enzmictec.2013.12.012. Epub 2013 Dec 22.
Escherichia coli L-asparaginases have great significance in the treatment of leukemia. Consequently, there is considerable interest in engineering this enzyme for improving its stability. In this work, the effect of surface charge on the stability of the enzyme l-asparaginase II was studied by site-directed mutagenesis of the cloned ansB gene from Escherichia sp. Replacement of two positively charged residues (K139 and K207) on the surface loops with neutral and reverse charges resulted in altered thermo stability in designed variants. Neutral charge substitutions (K139A and K207A) retained greater tolerance and stability followed by negative charge substitutions (K139D and K207D) compared to control mutant K139R and wild enzyme. From the results, it was concluded that the optimization of surface charge contributed much to the thermal properties of proteins without affecting the structure.
大肠杆菌L-天冬酰胺酶在白血病治疗中具有重要意义。因此，人们对改造这种酶以提高其稳定性有着浓厚兴趣。在这项工作中，通过对来自埃希氏菌属的克隆ansB基因进行定点诱变，研究了表面电荷对L-天冬酰胺酶II稳定性的影响。用中性和反向电荷取代表面环上的两个带正电荷的残基（K139和K207），导致设计变体的热稳定性发生改变。与对照突变体K139R和野生型酶相比，中性电荷取代（K139A和K207A）具有更高的耐受性和稳定性，其次是负电荷取代（K139D和K207D）。从结果可以得出结论，表面电荷的优化对蛋白质的热性质有很大贡献，而不影响其结构。
