Effect of salts on water-insoluble glucan formation by glucosyltransferase of Streptococcus mutans

Abstract

The formation of water-insoluble glucan by extracellular glucosyltransferase from Streptococcus mutans 6715 found to be greatly stimulated by various mono- or divalent cations. An enzyme preparation, obtained by ethanol fractionation, was able to catalyze the formation of water-insoluble glucan from sucrose in the presence of monovalent cations above 100mM or divalent cations above 20 mM at neutral pH. As the concentration of monovalent and divalent cations was reduced to below 10 mM and 1 mM, respectively, the formation of insoluble glucan decreased to a negligible amount. High concentrations of these cations were found to stimulate the formation of insoluble glucan in the following ways: (i) it increased the activity of total glucosyltransferase up to 1.6- and 2.7-fold in the absence and presence of a primer dextran, respectively, and (ii) it changed the formation of soluble glucan to insoluble. It was postulated that one of the essential factors for the formation of insoluble glucan would be to keep more than two water-soluble glucan chains close to enzyme aggregates and that such interaction could be enhanced by the presence of high cation concentrations.

Glucosyltransferases of Streptococcus sobrinus C211 are both stimulated and inhibited by hydrogen peroxide

“…The interconversion of GTF-S from soluble glucan synthesis to insoluble glucan synthesis has been documented (10,20,23,25). The conversion of GTF-S usually occurs under conditions where the enzyme tends to aggregate.…”

“…The conversion of GTF-S usually occurs under conditions where the enzyme tends to aggregate. GTF has been known to be altered in the presence of teichoic acids (28), phospholipids (31), high ionic strength environments (28) and high calcium levels (25). Hydrogen peroxide, on the other hand, has been shown to crosslink proteins.…”

Purification and Characterization of Extracellular Glucosyltransferase from Streptococcus mutans Serotype b (Subspecies rattus)

“…Enzyme assay. The enzyme activity was measured as previously reported (Mukasa et al, 1979) in 1 mlO.1 Msodium phosphate buffer (pH 6.5) or 0.1 M-sodium maleate buffer (pH 6.0) containing 41.8 mM-sucrose and 0.01 % Merthiolate with or without 0.34 mg dextran T10. The reaction was linear for at least 12 h under these assay conditions.…”

“…Polysaccharides were collected, washed as described by Mukasa et al (1979) and measured by the phenol/sulphuric acid method (Dubois et al, 1956), using glucose as a standard. Fructan was measured by &he method of Van Handel (1967) with some modifications as follows: 0-2 g anthrone was dissolved in a mixture of 95 ml concentrated sulphuric acid (18 M) and 5 ml distilled water, and subsequently added with 20 ml distilled water at 4 "C. A sample solution, adjusted to 0.5 ml with distilled water, and 3 ml of the anthrone reagent were mixed at 4 "C, and kept at 45 "C for 20 min.…”

Purification and properties of extracellular glucosyltransferase from Streptococcus bovis

“…Enzyme activity was determined as previously reported (16) with some modifications. Briefly, the reaction mixture contained 0.1 M sodium phosphate buffer (pH 6.5), 1% (W/V) sucrose, 0.01% Merthiolate, 0.1% Triton X-100, and enzyme solution in a total volume (2 ml).…”