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 essentialrole in the pathogenesis of dental caries. Enzymatically activeGtf is found in whole human saliva (solution), and incorporatedinto the salivary pellicle that is formed on teeth in vivo (surface).GtfB glucans are predominantly 1,3-linked; however, surface-formedglucans from GtfB contain greater amounts of 3-linked glucosethan glucans formed in solution. In contrast, the major linkageof glucans formed on the surface by GtfB in the presence ofsucrose and starch hydrolysates is 4-linked glucose. GtfC-derivedglucans in solution have a major linkage of 6-linked glucose,while surface-formed glucans from the same enzyme have 3-linkedglucose as the major linkage. GtfD glucans formed either insolution or on the surface are predominantly 1,6-linked; however,surface-formed glucans contain more 6-linked glucose than solution-formedglucans. Digestion with the glucanohydrolases mutanase and dextranaseshows differences in susceptibility among glucans formed eitherin solution or on the surface by each of the Gtf enzymes, anddifferences are also seen in the soluble end products from thesedigestions. Our results show that the same Gtf enzyme can formstructurally distinct glucans hi solution and on a surface.These observations are important in the study of naturally occurringmicrobial films. dextranase glucans glucosyltransferases mutanase structure