Heterologous expression and characterization of a novel mesophilic maltogenic α-amylase AmyFlA from Flavobacterium sp. NAU1659

Abstract

A novel amylase AmyFlA from Flavobacterium sp. NAU1659 was cloned and expressed in Esherichia coli. Analysis of the sequence homology exhibited that AmyFlA shared 98% identity with the putative protein belonging to glycoside hydrolase family 13 (GH13) from Flavobacterium sp., however, it had the sequence identity lower than 35% with the reported GH13 amylases. AmyFlA was consisted of 620 amino acids, with a putative signal peptide of 25 amino acids. The enzyme enabled to hydrolyze soluble starch into a high level of maltose, and showed a specific activity of 352.97 U/mg at 50°C in 50 mM phosphate buffer (pH 6.0). The Km and Vmax of AmyFlA was 3.15 mg/ml and 566.36 µmol·ml− 1·min− 1 under optimal condition, respectively. Moreover, compared to the reported maltogenic amylases, at the initial reaction, AmyFlA produced a less variety of intermediate oligosaccharides, in which contained a higher amount of maltose. These results indicated that AmyFlA possessed potential application values in high-maltose syrup production.