STRUCTURAL ASPECTS OF GLUCANS FORMED IN SOLUTION AND ON THE SURFACE OF HYDROXYAPATITE

Streptococcus mutans glucosyltransferases (GtfB, -C, and -D) and their products formed from sucrose, glucans, play an essential role in the pathogenesis of dental caries, Enzymatically active Gtf is found in wh ole human saliva (solution), and incorporated into the salivary pellic le that is formed on teeth in vivo (surface), GtfB glucans are predomi nantly 1,3-linked; however, surface-formed glucans from GtfB contain g reater amounts of 3-linked glucose than glucans formed in solution. In contrast, the major linkage of glucans formed on the surface by GtfB in the presence of sucrose and starch hydrolysates is 3-linked glucose , GtfC-derived glucans in solution have a major linkage of 6-linked gl ucose, while surface-formed glucans from the same enzyme have 3-linked glucose as the major linkage. GtfD glucans formed either in solution or on the surface are predominantly 1,6-linked; however, surface-forme d glucans contain more 6-linked glucose than solution-formed glucans, Digestion with the glucanohydrolases mutanase and dextranase shows dif ferences in susceptibility among glucans formed either in solution or on the surface by each of the Gtf enzymes, and differences are also se en in the soluble end products from these digestions, Our results show that the same Gtf enzyme can form structurally distinct glucans in so lution and on a surface, These observations are important in the study of naturally occurring microbial films.