Purification and Some Properties of an α-Glucosidase from Alkaliphilic Bacillus sp. Strain HM-127

Abstract

In this study, we isolated alkaliphilic Bacillus sp. strain HM-127 as the source of α-glucosidase. An analysis of the purified enzyme for molecular mass was carried out by SDS-PAGE, which revealed a single band (63 kDa). Maximum activity of the enzyme against maltose was at pH 6.4. When p-nitrophenyl-α-glucopyranoside (pNPG) was used as substrate, two pH optima, 6.4 and 8.3, were observed. The enzymatic activity was strongly inhibited by Fe²⁺, Zn²⁺ and ethylenediaminetetraacetic acid, when using both substrates. Phenylmethylsulfonyl fluoride and dithiothreitol almost completely eliminated the pNPG-hydrolyzing activity and maltose-hydrolyzing activity, respectively. At high concentrations of sucrose and turanose, the activity of the enzyme against pNPG was markedly inhibited at pH 8.3 but no inhibitory effect occurred at pH 6.4. The present results suggest that the Bacillus sp. strain HM-127 α-glucosidase hydrolyzes pNPG and maltose by different catalytic mechanisms at pH 6.4 and 8.3.