Further Characterization of Dormant Reaction of Cyclodextrin Glucanotransferase with Dextran and Subsequently Produced Dextran.

Abstract

Structurally modified dextran was produced by the action of cyclodextrin glucanotransferase (CGTase) on clinical dextran. The dormant activity of CGTase was further confirmed by using the enzyme preparation from a different source. Although an increase in reducing sugar in the reaction mixture was small, a clear difference in the molecular weight distribution of CGTase-treated dextran was observed, as in previous experiments. Therefore the susceptibility of CGTases on dextran was verified with the other origin of CGTase. CGTase-treated dextran showed a higher interaction with Con A and fluorescent reagent, 6-p-toluidinylnaphthalene-2-sulfonate. The susceptibility of CGTasetreated dextran to isoamylase and glucoamylase varied significantly according to the reaction temperatures for the CGTase action. NMR-HMQC and methylation analyses both indicated additional occurrence of α-1, 4-branch points in the dextran molecule, which opposed the knowledge of sole branch point of -1, 3-linkages in the dextran. CGTase action seemed to increase the content of α-1, 4-branch points in the CGTase- treated dextran by introducing the cleaved fragments as the new branch into the back bones of α-1, 6-linkages. These results suggested that CGTasetreated dextran had increasing amounts of α-1, 4-branch points, which caused the structural changes demonstrated by the above analysis.