Origin of branches in native dextrans.

Abstract

AbstractAccording to the proposed mechanism for the enzymatic formation of dextran, branches of different length are formed in a reaction between a so‐called acceptor dextran molecule and an active reaction complex; propagation of the dextran chain occurs by an insertion‐type polymer growth. To investigate this branching reaction, radioactive labeled acceptor dextran of relatively low molecular weight was added to a dextran synthesizing system and the native high molecular weight dextran separated by a fractionation method. From the specific radioactivity of the isolated native dextran, and assuming a molecular weight of 2.5 × 105, the average number of acceptor molecules incorporated into native dextran is calculated to be about unity, as predicted by the proposed mechanism. Analogous results have been obtained in the reaction of two different dextran sucrases from Leuconostoc mesenteroides B512F and B1307, respectively.