Characterization of glucan involved in the reduction of dental caries in rats.

Culture supernatant fluids (SF) of mutant 108 obtained from Streptococcus sobrinus 6715, when incubated with sucrose, produce large amounts of water-soluble glucans. Mainly, two water-soluble glucan synthesizing glucosyltransferases (GTases) were found in culture SF by isoelectric focusing. These two GTases had higher activities than those from the parent strain. The GTase which synthesizes water-insoluble glucan totally lacked the mutant. When the glucan preparation synthesized by the SF was subjected to gel filtration, a major large molecular weight fraction (designated glucan A) and a small molecular weight fraction (designated glucan B) were obtained. Glucan A yielded a smaller molecular weight glucan after treatment with dextranase. Glucan B was not hydrolyzed by the same enzyme.