Enzymes that hydrolyze pullulan (1), such as pullulanases [1,2], isopullulanase [3], neopullulanases [4][5][6], and Thermoactinomyces vulgaris alpha-amylases [7,8] are useful in the production of various oligosaccharides from starch or pullulan . Recently, because of the commercial significance, many of their amino acid sequences have been reported. Comparisons between the amino acid sequences and the substrate specificities may provide clues about their pullulan-hydrolyzing mechanism.
Oligosaccharides with a-(1 -)-6)-glucosidic linkages are indispensable for the study of their substrate specificities . Thermoactinomyces vulgaris R-47 produces two alpha-amylases, TVA I and TVA II, which hydrolyze a-(1--> 4)-glucosidic linkages of 1 to produce panose (2) . These enzymes can hydrolyze not only a-(1 -4)-glucosidic linkages of 1, but also the a-
Thus they should also transglycosylate both a-(1 -44)-and a-(1 -' 6)-glucosidic linkages . Similar reactions have been reported in neopullulanase [4] and Bacillus licheniformis alpha-amylase [9]. In this paper, we report convenient methods of preparing 4 2-a-isomaltosylisomaltose (4) using TVA II .
We used a mixture of 1 and glucose as the starting materials . In this system, TVA II should produce a hydrolysate (2) and two tetrasaccharides, 6 3-a-gluco-* Corresponding author .