Characterization of novel thermophilic alpha-glucosidase from Bifidobacterium longum

Abstract In this study, the gene encoding α-glucosidase from Bifidobacterium longum subsp. longum JCM1217 (BLAG) was cloned and expressed in Escherichia coli . The amino acid sequence alignment demonstrated that BLAG belongs to glycoside hydrolase (GH) family 13. The optimal temperature for enzyme activity was 75 °C; about 80% of the catalytic activity was lost at 50 °C, which is very unusual for enzymes from the Bifidobacterium genus. In the presence of 5 mM of Co 2+ and Ca 2+ , enzyme activity was reduced to 47% and 48%, respectively. Furthermore, BLAG lost catalytic activity following the addition of 5 mM of Fe 2+ ion. The BLAG enzyme was able to hydrolyze α-1,2, α-1,3, α-1,4, and α-1,6 glycosidic O -linkages and liberated glucose from the non-reducing end of substrates. The kinetic study revealed that among the maltooligosaccharides, BLAG showed the highest k cat / K m value to maltotriose (G3), and had relatively low k cat / K m values on long-chain maltooligosaccharides. This is the first report describing the production of a thermophilic α-glucosidase from the Bifidobacterium genus.