Synthesis of levan by levansucrase. Some factors affecting the rate of synthesis and degree of polymerization of levan.

The addition of levan as a so-called "acceptor" accelerated the rate of polymerization of levan catalyzed by levansucrase [EC 2.4.1.10]. However, this effect was seen only under conditions of low ionic strength. Under conditions of high ionic strength, only levan with an average degree of polymerization (DP) of 120 was synthesized with a reasonable yield. Incorporation of [14C]fructose residues into levan of high molecular weight (DP 1,200) added as an "acceptor" at high ionic strength was slight. It is suggested that the DP of levan synthesized is generally regulated by ionic strength, and that enzymic synthesis of levan occurs in the absence of an "acceptor."