Purification and Properties of Glucosyltransferase Produced by Streptococcus salivarius HHT

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Glucosyltransferase produced by Streptococcus salivarius HHT was purified from the culture filtrate, and its enzymic properties were examined. The enzyme was specific to sucrose (Km 7.2mM), and formed a water-insoluble α-D-glucan consisting of a high proportion of (1 → 3)-α-D-glucosidic linkage (90%) together with small proportions of (1 → 6)- and (1 → 4)-α-D-glucosidic linkages. The optimum pH and temperature of the enzyme activity were 5.8 and 40°C, respectively. The enzyme activity and yield of the water-insoluble glucan were stimulated in the presence of dextran. The addition of low molecular weight oligosaccharides, such as maltose and isomaltose, inhibited the production of the water-insoluble glucan with the concomitant formation of several oligosaccharides, i.e., O-α-D-glucopyranosyl-(1 → 6)-O-α-D-glucopyranosyl-(1 → 4)-D-glucopyranose (panose), O-α-D-glucopyranosyl-(1 → 3)-O-α-D-glucopyranosyl-(1 → 4)-D-glucopyranose, maltotriose, and O-α-D-glucopyranosyl-(1 → 6)-O-α-D-glucopyranosyl-(1 → 6)-O-α-D-glucopyranosyl-(1 → 4)-D-glucopyranose.