Abstract
Two α-glucosidases, which hydrolyzed 4-nitrophenyl (4NP)-α-D-glucopyranoside, were purified and characterized from Bifidobacterium longum subsp. longum JCM 7052 grown on gum arabic. These enzymes, named BlAglA1 and BlAglA2, had apparent molecular masses of 72.0 and 72.8 kDa estimated by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and 70.1 and 92.7 kDa by PAGE without SDS, respectively. The amino acid sequences analyzed by MALDI-TOF-MS were found in the genomes of several strains of B. longum subsp. longum . BlAglA1 and BlAglA2 showed hydrolyzing activities toward isomaltose, trehalose, palatinose, isomaltotriose and panose, but did not toward sucrose, maltose, amylose, amylopectin, and oyster glycogen, indicating that each enzyme belongs to oligo-1,6glucosidase (EC 3.2.1.10). Both enzymes showed optimal activities with 4NP-α-D-glucopyranoside at pH 5.5-6.0 and at 45-50°C. Values of K m and V max
for 4NP-α-D-glucopyranoside, trehalose, palatinose, panose, isomaltose, and isomaltotriose were also determined. The two oligo-1,6-glucosidases were shown to have transglycosylation activities to synthesize oligosaccharides from trehalose, palatinose, isomaltose, panose, and isomaltotriose to their selves. Both enzymes also catalyzed transglucosylation from palatinose to ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-hexanol.
