Abstract
Transglycosylation reactions catalyzed by the fungal p-transglycosylases as well as the bacterial fructosyltransferase are reviewed with respect to their mechanisms and specificities in the biosynthesis of corresponding oligo- and polysaccharides. β-Transglycosylases (β-TG) of Sclerotinia libertiana . and Trichoderma longibrachiatum catalyzed the intermolecular transglycosylation using cellooligosaccharides as both glycosyl donors and acceptors. High molecular weight components synthesized by the reactions were identified as linear β-1, 4-glucans having average d. p. of 14 or more. Both enzymes were defined as new enzymes with a disproportionating activity on β-1, 4-glucosidic linkage. Interaction of β-TG with native cellulose fiber was demonstrated in the enzyme of T. longibrachiatum, suggesting its functional contribution to the fungal cell wall synthesis. The manner of fructosyl transfer by Bacillus subtilis levansucrase was easily modified with the environmental conditions. The enzyme showed jS-fructosidase-like activity, catalyzing the hydrolysis of sucrose at a high temperature as well as the fructosyl transfer to the acceptor molecule when it was present at a high concentration. The enzyme lost the ability to synthesize highly branched levan of high molecular weight in the mixture with high ionic strength where it preferably synthesized low molecular weight levan of 4 or 5 branches.
