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.