Studies on the enzymatic systhesis of dextran from sucrose.

The syntheses of dextrans (l-5) and levans (6-10) from sucrose by enzymes from certain bacteria and the syntheses of glycogens and starches from glucose-l-phosphate by phosphorylases from yeast (11) and animal (12-15) and plant (16, 17) tissues have a fundamental point of similarity in that, with all of them, the substrate contains the basic unit of the final polymer product in the form of a glycoside radical (5). A point of difference from the glycogen and starch syntheses is that phosphorylated compounds apparently are not required in the syntheses of dextrans and levans (5, 8). A further distinction is that the enzymatically synthesized dextrans and levans that we have studied (1, 2, 4, 9) are serologically active; this feature, although not representing a fundamental difference in the syntheses themselves, is of special interest to the bacteriologist, and has been utilized to particular advantage in examining the question of the likeness between the polysaccharides synthesized by the cell-free enzymes and the natural polysaccharides formed in the living bacterial cultures (2, 4). The present paper deals with some aspects of t.he kinetics of dextran formation from sucrose by enzymes from a. strain of Leuconostoc mesenteroides. Previous papers (1, 2, 4, 5) included data indicating that this enzymatic reaction consists of the conversion of n molecules of sucrose to a polymer of n glucose anhydride units plus n molecules of fructose, and also data showing that the enzymatically synthesized dextran agreed in serological as well as in chemical properties with the dext,ran elaborated in living cultures of the bacteria from which the enzymes were derived. The present object is to present data on the equilibrium point, velocity constants, and ot#her aspects of the reaction, which could be studied more adequately with t’he more potent enzyme preparat,ions described in this paper than with the enzyme preparations utilized in the previous studies.