Partial characterization of the glucosyltransferases of an oral Streptococcus salivarius strain

The oral Streptococcus salivarius strain S3 possessed extracellular glucosyltransferase (GTF) and cell-associated fructosyltransferase activities. Chromatofocusing column chromatography of crude GTF yielded multiple peak fractions, which were categorized into two types which catalysed (1) water-insoluble glucan synthesis and (2) water-soluble glucan formation. The GTF isozyme eluted in fraction 29 synthesized mutanase- and dextranase-sensitive insoluble glucan from sucrose, while fraction 81 GTF synthesized soluble glucan which was insensitive to both glucanases. The ability to agglutinate Streptococcus sobrinus cells was high for insoluble glucan but negligible for soluble glucan. The insoluble glucan-synthesizing activity of fraction 29 GTF was inhibited by the presence of dextran T10. Isoelectric focusing yielded a single activity band but SDS-polyacrylamide gel electrophoresis gave multiple bands for both GTF fractions 29 and 81. The extracellular crude GTF activity was inactivated by 0.1% SDS or 1% Tween 80, but the activity was completely restored by the addition of 1% Triton X-100.