Interpretation of dextransucrase inhibition at high sucrose concentrations.

When acceptor reactions were carried out at high sucrose concentrations (> or = 200 mM), dextran synthesis was inhibited and the acceptor reactions were increased. A model, based on the known mechanisms of dextran synthesis and acceptor reactions, is proposed to explain the inhibition of dextran synthesis and the increase in the acceptor products at high sucrose concentrations. According to the model, sucrose binds to a third, low-affinity binding site, allosterically changing the conformation of the active site so that dextran cannot be formed but acceptor products can be formed.