EN
Mutans streptococci Streptococcus mutans and S. sobrinus play central role in the etiology of human dental caries due to their acidogenic potential and ability to form extracellular water-insoluble and water-soluble glucans in the presence of dietary sucrose. Streptococcal glucans are synthesized by a constitutive group of extracellular and/or cell-associated enzymes showing glucosyltransferase (GTF) activity. Each enzyme has distinctive properties, varying in its requirement for a glucan primer molecule, the proportion of alpha(1-6)- and alpha(1-3)-linkages, the degree of branching it introduces into the glucan, and the total length of glucan chain produced. Moreover, the overall properties of glucan depend on the relative activity of different GTF enzymes, as well as on their interactions, since one GTF may modify the product of another. This review article presents recent trends in the investigations on streptococcal GTFs and glucans. Particular emphasis has been laid on catalytic properties and molecular structure of different GTFs and on the mechanism of synthesis of specific glucans. Furthermore, the role of these enzymes and their products in the pathogenesis of dental caries is also discussed.