The interaction of enzymatically active glucosyltransferase with host-derived constituents of the acquired enamel pellicle, as well as the products of GTF activity, may play a profound role in the formation and maturation of dental plaque. Glucosyltransferase adsorbs preferably to salivary-coated hydroxyapatite (sHA) in vitro and in vivo and expresses greatly enhanced glucan synthesizing ability. Results from studies in our laboratory indicate that glucosyltransferase expresses catalytic activity over a broad range of pH (4.5-7.5) and temperature when compared with the enzyme in solution. Glucan synthesized in situ adheres strongly to the sHA surface and provides binding sites for Streptococcus mutans and Streptococcus sobrinus. The clinical relevance of these data is enhanced by the observation that an amino alcohol which is without effect on the enzyme in solution effectively inhibits the enzyme adsorbed to a surface. To explore these important phenomena further, we propose to determine whether the different GTF enzymes produced by S. mutans (GTF-I, GTF-SI, GTF-S) differ in their ability to adhere to sHA. We will use enzymes prepared from an organism into which the genes have been cloned, thereby rendering purification of the enzymes less difficult. In addition, using gel electrophoresis and antibodies, we will examine specifically the constituents in saliva with which the GTF interacts. By means of cross-linking, we will attempt to identify the peptides in GTF that react with salivary constituents and use the information generated to biologically prepare peptides that can be used to compete with GTF for binding sites on sHA, thereby providing additional insight to the nature of these interactions and possibly pointing the way to development of antiplaque agents. We will examine the structure, molecular weight, and solubility of the glucans formed in situ. Such information may make it possible to design molecules which will compete with S. mutans and certain actinomyces for sites on glucan-coated pellicle.
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