Involved in the production of dextran, an extracellular glucan polymer. [(1->6)-alpha-D-glucosyl](n) + sucrose = [(1->6)-alpha-D-glucosyl](n+1) + D-fructose The dextran produced by Leuconostoc mesenteroides CMG713 has a molecular mass of about 2000 kDa and contains exclusively alpha-(1->6) glycosidic linkages in the main chain. Belongs to the glycosyl hydrolase 70 family.