The dextran acceptor reaction of dextransucrase from Streptococcus mutans K1-R.

Soluble dextransucrase activity(ies) was eluted with a solution of clinical dextran from the insoluble dextran--cell complex produced by Streptococcus mutans K1-R grown in the presence of sucrose. Studies of the dextran acceptor-reaction of the soluble enzyme-preparation indicate that it is highly specific for dextran of high molecular weight. Increased dextran synthesis in the presence of dextran acceptor and the apparent inhibition of this stimulation by higher concentrations of dextran result from product modification rather than a direct effect on the level of enzyme activity. The results demonstrate that the potentially water-insoluble structure synthesized by dextransucrase on exogenous, soluble dextran acts as a more-efficient acceptor than the soluble dextran. The role of the acceptor reaction in the biosynthesis of complex dextrans is discussed.