| 英文摘要 |
Enzymatic transglycosylation takes place between an oligosaccharide donor and a relatively large number of structurally diverse acceptor molecules such as bioactive natural compounds. The enzymes including maltogenic amylase (MAase), α-glucanotransferase (α-GTase), and cyclodextrin glucanotransferase (CGTase) are involved in this transglycosylational bioconversion. We have investigated the biotechnological modification of natural compounds such as isoflavones by transglycosylation activity of MAase. MAases catalyze not only hydrolysis of substrate, but also transglycosylation reaction in the presence of various acceptor molecules by preferentially forming α-(1,6)-glycosidic linkage. The mechanism of transglycosylation was elucidated on the basis of three-dimensional structure and site-directed mutagenesis. The results suggested that Glu-332, which is located in a pocket, plays an important role on the formation and accumulation of transfer products by aligning the acceptor molecule in the nucleophilic attack of the glycosyl-enzyme intermediate. In vitro MAase is capable of transferring glucosyl moiety of donor molecules to acceptor such as genistin and puerarin to give an α-(1,6)-glycosidic linkage. We found that transglycosylation reactions have successfully increased the water solubility and the water-soluble products fully maintained the biological activities. In this presentation, some potential applications of the transglycosylated bioactive products in food industry will be discussed. |
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