Characterization of some enzymatic properties of recombinant α-glucosidase III from the Thai honeybee, Apis cerana indica Fabricus
Recombinant α-glucosidase III (rHBGase III) from Apis cerana indica Fabricus (rAciHBGase III) was expressed in the yeast Pichia pastoris GS115, enriched and characterized. The full length cDNA of AciHbgase III (ƒî1.8 kb) was amplified by RT-PCR, cloned into the pPICZαA expression vector and used to transform P. pastoris GS115. The maximum secreted expression level of rAciHBGase III [as an N terminal (His)6 tagged chimera] was found 144 h after induction by 1% (v/v) methanol. Enrichment of the enzyme using histrap affinity purification revealed a single active glucosidase band with a molecular mass of ~68 kDa. The optimal pH and temperature for glucosidase activity of the enriched rAciHBGase III were pH 5.0 and 37¢XC, respectively, whilst the enzyme showed a good pH stability between pH 5.0 to 7.5, but not below pH 5.0, and a poor thermotolerance with < 10% and 0% residual activity at 40 and >50¢XC, respectively. The rAciHBGase showed a relatively high substrate specificity for maltose (Km of 4.5 mM) and p-nitrophenyl α-D-glucoside (Km of 4.4 mM) compared to other reported HBGase enzymes.
Key words: α-Glucosidase, Apis cerana indica, expression, kinetics, recombinant enzyme.