The dextransucrase produced by Streptococcus bovis 148 was purified about 20.8-fold to electrophoretic homogeneity (specific activity 246.3 units/mg) from the culture supernatant. Molecular weight of the native enzyme was estimated to be 600 kDa, whereas the molecular weight per subunit was 150 kDa. The dextran synthesized consisted chiefly of alpha-1,6-glucosidic linkage, containing small numbers of branches that had the alpha-1,3-glucosidic linkage.