Nucleotide sequence of the dextran glucosidase (dexB) gene of Streptococcus mutans.

Nucleotide sequencing of DNA in the region of the Streptococcus mutans chromosome adjacent to the previously characterized gtfA gene revealed the presence of two long open reading frames. One of these corresponds to the dexB gene and has been shown to encode an intracellular exodextranase (dextran glucosidase) which has short isomaltosaccharides as preferred substrates. Comparison with other published sequences showed that the dexB gene product shares regions of similarity with enzymes, from a variety of sources, which attack other glucose polymers.