During the studies on application of amylases, some a-amylases showed a remarkable transglycosylation action in a high concentration of starch. Using the action, the production of novel and useful saccharides was undertaken, and CGTase was selected. The enzyme catalyzes “cyclization” forming cyclodextrins, “disproportionation” and “coupling reaction, ” in which glycosyl residues are transferred from α-1, 4-glucan or cyclodextrins to an acceptor such as glucose or sucrose. Through the coupling reaction of CGTase we succeeded in the conjugation with glycosyl residue and various substances, and established their usages in food industry and related fields.