Control of the synthesis of dextran and acceptor-products by Leuconostoc mesenteroides B-512FM dextransucrase.

In the maltose-acceptor reaction of Leuconostoc mesenteroides B-512FM dextransucrase, some of the D-glucose moieties of sucrose are diverted from the synthesis of dextran and are transferred to the nonreducing end of maltose to form panose. Glucose is also transferred to panose and to subsequent acceptor products to give a homologous series of isomaltosyl dextrins attached alpha-(1-->6) to maltose. Three experimental parameters were studied to obtain quantitative information about the yield and distribution of acceptor products and the yield of dextran: (a) the ratio of maltose to sucrose, (b) the concentration of maltose and sucrose, and (c) the amount of enzyme. The reactions were run with [14C]sucrose and the amount of each acceptor product and the amount of dextran synthesized were determined for (a), (b), and (c) by TLC separation and measurement of the radioactivity with a PhosphorImager. It was found that an increase in the ratio of maltose to sucrose increased the amount of acceptor products with a concomitant decrease in the synthesis of dextran. Further, as the ratio was increased, the number of acceptor-products decreased. When the concentrations of maltose and sucrose were increased and the ratio was maintained at 1:1, there also was a decrease in the amount of dextran and an increase in the amount of acceptor-products. In addition, there was a decrease in the amount of dextran and an increase in the amount and number of acceptor-products when the amount of enzyme was increased. The first acceptor-product can be exclusively obtained without the formation of any dextran, by using a specific ratio and concentration of maltose and sucrose and a specified amount of enzyme.