A-Transglucosidase

A product manufactured in Japan as Alo mixture (Anomalously Linked Oligosaccharides) contains mainly a range of IMOS (glucose, isomaltose, and panose as principal constituents). It is produced from starch as substrate by the action of alpha-amylase, beta-amylase, and a transglucosidase. It is claimed to have favorable properties for application in the food industry.143... 

The use of a-transglucosidases in the large-scale manufacture of novel bioderivatives is stiU limited by several factors such as enzyme selectivity, stability, and, in some cases, efficiency. To overcome these Umitations and further enlarge the appUcatimis of these enzymes, the latest protein engineering technologies have been used to tailor biocatalysts with specific properties for novel oligosaccharide. 

The so-called Q-razyme is a transglucosidase which converts one in every twenty 1-4 linka es of amylose into 1-6 linkages to form a branched chain. The enzyme only acts when at least forty-two glucose residues have been imited to form amylose. The formation reaction is the following ... 

Like the branching enzyme, the Q-enzyme acts like a transglucosidase capable of forming 1-6 bonds. 

It appears that an identical polysaccharide is formed in the same organism by two different enzymatic mechanisms, namely one involving a transglucosidase and the other a phosphorylase. 

Wallenfels, using another strain of AspergiUus oryzae, also obtained a transglucosidase which forms similar oligosaccharides from maltose. 

Wu, P.-H., Nair, G.R., Chu, I.-M. and Wu, W.-T. (2008) High cell density cultivation of Escherichia coli with surface anchored transglucosidase for use as whole-cell biocatalyst for a-arbutin synthesis. Journal of Industrial... 

Sucrose phosphorylase can then be regarded as a rather versatile transglucosidase, capable of exchanging glycosidic and ester bonds and of donating D-glucose to a variety of substrates such as ketoses, an aldose, inorganic phosphate and arsenate. 

As bacterial transglucosidase is instrumental in the transfer of a D-glucose residue from one acceptor to another, so does yeast hexokinase 3 catalyze a transphosphorylation. The highly specific donator of a labile phosphate group is adenosine triphosphate (XX), the fermentable hexoses D-glucose, D-mannose and D-fructose functioning as acceptors. Hexokinase catalyzes the reaction... 

Fig. 2 Main reactions catalyzed by sucrose-utilizing transglucosidases. The synthesis of a-glucans (Glc) linked through either a-1,6 a-1,3, a-1,4, or a-1,2 osidic linkages depending on the enzyme specificity is obtained by glucansucrases. The formation of a-D-glucose-1-phosphate from orthophosphate is obtained using sucrose-phosphorylases. The mechanism involves a double-inversion at the anomeric center via the formation of a covalent P-D-glucosyl enzyme intermediate...

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