New reactions of dextransucrase: α- d-glucosyl transfers to and from the anomeric sites of lactulose and fructose

Both acceptor and donor specificities of dextransucrase have been found to be broader than hitherto supposed. Preparations from different strains of L. mesenteroides readily catalyzed energy retentive α- d-glucosyl transfers to the hemiacetal hydroxyls of free and 0-β- d-galactosyl-substituted β- d-fructofuranose e.g., sucrose + lactulose ⇌ 4 F-β-galactosylsucrose + fructose. In addition, they utilized 4 F-β-galactosylsucrose (lactulosucrose) almost as effectively as sucrose for the synthesis of immunologically specific, high polymer dextran. Differences in capacity for sucrose bond synthesis vs. dextran synthesis among the preparations make it appear likely that a family of dextransucrases, differing in relative affinity for the various glucose carbinols of growing dextran chains, may account for the structural diversity of dextrans from different biological sources.