Inhibition of dextran and mutan synthesis by cycloisomaltooligosaccharides.

Novel cyclic isomaltooligosaccharides, cyclodextran, strongly inhibited the dextransucrase reaction. The inhibition was dependent on the cyclodextran concentration and greatly enhanced by the first incubation at 30 degrees for 30 min. Cyclodextran-heptaose and -octaose were competitive inhibitors for sucrose yielding Ki's of 0.25 and 0.64 mM, respectively. Both reducing sugar and dextran producing activities of dextransucrase were almost equally inhibited by the cyclodextrans. Although gamma-cyclodextrin, palatinose, sucrose-monocaprate, and maltitol gave 5-35% inhibition, cyclodextran-heptaose gave 95% inhibition. Moreover, water-insoluble glucan (mutan) synthesis by the glucosyltransferase from Streptococcus mutans was significantly repressed by the addition of cyclodextran.