Characterization of an anti-glucosyltransferase serum specific for insoluble glucan synthesis by Streptococcus mutans.

An anti-glucosyltransferase serum, which synthesized 96% insoluble glucans, was prepared against a purified enzyme preparation from Streptococcus mutans strain HS6 (serotype a). This serum was examined for its effects on glucan synthesis by crude enzyme preparations from eight strains (four serotypes) of S. mutans and for the ability of these preparations to promote adherence of S. mutans to a smooth surface. Glucosyltransferase activity was assayed by measuring the incorporation of glucose from [14C]glucose-labeled sucrose into water-insoluble and water-soluble (ethanol-insoluble) glucans. Anti-glucosyltransferase serum inhibited insoluble glucan synthesis by crude enzyme preparations from cells of the four serotypes of S. mutans. Enzymes from strains of types a, b, and d were inhibited between 70 to 90%; enzymes from type c strains were inhibited from 45 to 60%. The adherence to a glass surface of heat-killed cells from these four serotypes was likewise inhibited. Soluble glucan synthesis was not inhibited by the serum, and in some cases its synthesis increased as insoluble glucan synthesis decreased.