Preparation and Properties of Enzymically Synthesized Dextran

The most active extracts were obtained from L. mesenteroides cultures containing sucrose extracts prepared from L. mesenteroides organisms repeatedly transferred through D-glucose broth were of low potency. Active extracts in dilutions of 1 2 or 1 4 produced dextran in 5% sucrose solutions after one to two hours at 23°, and at pH 5.6 with acetate buffer demonstrable amounts of dextran were produced after twenty days with 1/10,000 dilution of the extract. Optimal yields of dextran were less than 5% based on sucrose. Small concentrations of dextran were detected by means of precipitin titrations with pneumococcus antisera Types II or XX (see page 215). 

This enzymically synthesized dextran differed from that formed by 

mesenteroides organisms only in its lower relative viscosity. Both types of dextran are serologically similar (see page 215). Each reacts with antisera of Leuconostoc and of pneumococcus Types II, XX, and XII, and comparable ratios of activity against these antisera were observed. 

Similar antisera absorption reactions were also obtained with each dextran. 

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Several species of streptococci are reported > to produce dextransucrases, although in many instances the n-glucans synthesized by these enzyme preparations have not been rigorously characterized as dextrans. The properties of streptococcal dextransucrases are somewhat different from those of Leuconostoc species synthetic activities are exhibited over a pH range of 5-8.5, and between 37 and 45°. Above all, the enzymes are constitutive and may, therefore, be obtained free from contamination by dextran. 

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