Resolution, purification, and characterization of two extracellular glucohydrolases, α-glucosidase and maltase, of Bacillus licheniformis

Abstract

Two extracellular α-glucosidases (EC 3.2.1.20, α-D-glucoside glucohydrolase) of Bacillus licheniformis NCIB 8549 were separated, purified, and partially characterized. Resolution of the complex into two separate enzymes was achieved using Sephadex G-150. The first of these activities, a maltase, hydrolysed maltose preferentially. It had slight activity on isomaltose, p-nitrophenyl-α-D-glycopyranoside, and sucrose. The pH optimum was 6.0 and the molecular weight determined on Sephadex G-200 was 160 000. This enzyme did not display any transglucosylation activity. The second enzyme was an α-glucosidase. It displayed highest activity on p-nitrophenyl-α-D-glucopyranoside, followed by isomaltose, sucrose, and maltose. As with the maltase, the pH optimum was 6.0 and the molecular weight as determined on Sephadex G-150 was 66 000. With isomaltose and maltotriose as substrates, transglucosylation activity was evident.