Metabolism of the reserve polysaccharide of Streptococcus mitis. Properties of α-(1→6)-glucosidase, its separation from transglucosylase, and the action of the two enzymes on branched oligosaccharides

Abstract

An [alpha]-(1[forward arrow]6)-glucosidase was separated from cell extracts of S. mitis. The enzyme was freed from transglucosylase by adsorption ofthe latter on retrograded amylose. The enzyme was detected in 5 of the 6 strains of S. mitis that were studied; [alpha]-(1[forward arrow]6)-glucosidase was not found in strain RB 1633, a strain that did not store polysaccharide. The glucosidase could act on compounds in which [alpha]-glucose is joined through an a -(1[forward arrow]6) -bond to either a maltosaccharide or an isomaltosaccharide. 62-[alpha]-Glucosylmaltose (panose) and 63-[alpha]-glucosylmaltotriose were hydrolyzed more rapidly and isomaltodextrins more slowly than isomaltose. Transferring activity towards isomaltose and panose was appreciable when the concentration of substrate was 2% or higher. The enzyme had no action on [alpha]-(1[forward arrow]4)-glucosidic linkages, [alpha] -Maltodextrinylglucoses were hydrolyzed only after transglucosylase action had attenuated them to isomaltose.