Date of this Version
The Streptococcus mutans serotype c gtfA gene encodes a 55-kilodalton sucrose-hydrolyzing enzyme. Analysis of S. mutans gtfA mutants revealed that the mutant strains were specifically impaired in the ability to use melibiose as a sole carbon source. S. mutans gafA mutant strains synthesized less α-galactosidase activity inducible by raffinose than wild-type strains. Melibiose (an inducer in wild-type strains) failed to induce significant levels of a-galactosidase in the mutant strains. We hypothesize that melibiose use by . mutans requires the interaction of the GtfA enzyme, or another gene product under the control of the gtfA promoter, with other gene product(s) involved in melibiose transport or hydrolysis.