Sucrose dextran synthesis

Fructose (from sucrose) is also involved in dextran synthesis in bacteria. 

All these oligo- and polysaccharides in nature are synthesized in vivo) via sucrose. Technical synthesis (in vitro) found industrial practices mainly for oligofructose, Neo-amylose and dextran following the reaction pathways as outlined in Figure 9.3.7. 

The structures of the dextrans may be controlled by the type of enzyme preparation employed, by the type of initial receptor molecules, or by the addition of branched low-molecular-weight dextrans which produce products of low molecular weight 178), Some dextrans appear to have D-fruc-tose end groups which are introduced into the molecule by sucrose acting as a receptor to initiate dextran synthesis. 

L. mesenteroides also contains a sucrose phosphorylase. However, since it has been demonstrated that sucrose is converted to dextran by dex-transucrase in the absence of a detectable quantity of inorganic phosphate and that the enzyme does not form polysaccharide from glucose-l-phos-phate, it is clear that phosphorylase is not involved in dextran synthesis. The evidence indicates that the dextransucrase acts by a direct transfer of glucose units. The reaction appears to involve the substitution of a 1,6-glucosidic linkage for a glucose-fructose bond and can be represented by. the following equation ... 

It is of interest that similar enzymes, capable of exchanging glycosidic linkages, appear to be involved in the synthesis of some polysaccharides. Thus the polysaccharide dextran is formed from sucrose by enzyme preparations from Leuconostoc46 while the polysaccharide levan is produced from sucrose or raffinose by enzymes of other bacteria.49 The reactions may be written as follows ... 

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