Activity of Streptococcus mutans alpha-D-glucosyltransferases released under various growth conditions

The effect of a variety of growth conditions on extracellular D-glucosyltransferase (GTF) activity of Streptococcus mutans strains in continuous culture has been studied. Maximum GTF activity was found at low growth rates and at pH 6.5, and under this condition the predominant glucosyltransferase was GTF-S, an enzyme that synthesized soluble dextran. At high growth rates, the proportion of GTF-S decreased, and 50% or more of the total glucosyltransferase was GTF-I, an enzyme that synthesized water-insoluble (1 leads to 3)-alpha-D-glucan. Variation in the relative activities of GTF-S and GTF-I results in such diversity in the glucans synthesized from sucrose that it is virtually meaningless to describe a structural analysis of S. mutans glucan without specifying the conditions of growth of the organism.