A thermostable α-amylase (designated as Amy16) has been previously identified in Flammeovirga pacifica isolated from deep-sea sediments. The DNA sequence of Amy16 exhibited no significant similarity with those of any known protein, including the glycoside hydrolases. Amino acid sequence analysis revealed that Amy16 belonged to GH13 family and possessed a conserved DXEXD motif, which was essential for its hydrolysis activities. The recombinant Amy16 purified with Ni(+) affinity column after its heterologous expression in Escherichia coli cells was most active at 50 °C and retained more than 81% of its initial activity after incubation at 60 °C for 20 min. The optimal pH for Amy16 was determined to be 6.5, and a good tolerance to alkaline environment was observed. Low concentration of Mg(2+), Sr(2+), Na(+) and K(+) slightly increased the activity of Amy16. Results of thin layer chromatography experiments revealed that Amy16 was able to hydrolyse starch into maltose in a time-dependent manner, suggesting that Amy16 is a liquid-type endoenzyme with starch hydrolysis activities. Therefore, our study presented thermostable and alkali-stable Amy16, which may be suitable for use as an additive in detergents.
Keywords: Alkali-stable; Deep-sea; Flammeovirga pacifica; Thermostable; α-Amylase.
Copyright © 2015 Elsevier B.V. All rights reserved.