Background: Nε-acetyl L-α lysine is an unusual acetylated di-amino acid synthesized and accumulated by certain halophiles under osmotic stress. Osmolytes are generally known to protect proteins and other cellular components under various stress conditions.

Objective: The structural and functional stability imparted by Nε-acetyl L-lysine on proteins were unknown and hence was studied and compared to other commonly known bacterial osmolytes - ectoine, proline, glycine betaine, trehalose and sucrose.

Methods: Effects of osmolytes on the temperature and pH profiles, pH stability and thermodynamic stability of the model enzyme, α-amylase were analyzed.

Results: At physiological pH, all the osmolytes under study increased the optimal temperature for enzyme activity and improved the thermodynamic stability of the enzyme. At acidic conditions (pH 3.0), Nε-acetyl L-α lysine and ectoine improved both the catalytic and thermodynamic stability of the enzyme; it was reflected in the increase in residual enzyme activity after incubation of the enzyme at pH 3.0 for 15 min by 60% and 63.5% and the midpoint temperature of unfolding transition by 11°C and 10°C respectively.

Conclusion: Such significant protective effects on both activity and stability of α-amylase imparted by addition of Nε-acetyl L-α lysine and ectoine at acidic conditions make these osmolytes interesting candidates for biotechnological applications.

背景：Nε-乙酰基L-α赖氨酸是一种不寻常的乙酰化二氨基酸，由某些嗜盐菌在渗透压下合成和积累。众所周知，渗透压可在各种压力条件下保护蛋白质和其他细胞成分。

目的：未知Nε-乙酰基L-赖氨酸对蛋白质的结构和功能稳定性，因此进行了研究和比较，并将其与其他常见的细菌渗透剂-外泌素，脯氨酸，甘氨酸甜菜碱，海藻糖和蔗糖进行了比较。

方法：分析渗透压对模型酶α-淀粉酶的温度和pH分布，pH稳定性和热力学稳定性的影响。

结果：在生理pH值下，所有被研究的渗透物均提高了酶活性的最佳温度，并提高了酶的热力学稳定性。在酸性条件下（pH 3.0），Nε-乙酰基L-α赖氨酸和ectoine可以提高酶的催化稳定性和热力学稳定性。这反映在将酶在pH 3.0下孵育15分钟后残留酶活性分别增加了60％和63.5％，以及展开转变的中点温度分别增加了11°C和10°C。

结论：在酸性条件下添加Nε-乙酰基L-α赖氨酸和ectoine赋予了对α-淀粉酶活性和稳定性的显着保护作用，这些渗透剂成为生物技术应用的有趣候选物。