The thermostable alpha-galactosidase from Candida guilliermondii H-404 synthesized self-transfer products in the absence of a suitable acceptor. The main self-transfer product, using melibiose as a donor substrate, was O-alpha-D-galactosyl-(1,6)-O-alpha-D-galactosyl-(1,6)-D-glucose. This enzyme had a wide acceptor specificity. D-Glucose, D-galactose, maltose, maltitol, and 1,4-butandiol were the most effective acceptors in the transgalactosylation catalyzed by this enzyme. The enzyme could also transfer alpha-galactosyl residues to pentoses (L-arabinose, D-xylose, and D-ribose) and methyl pentoses (D-fucose and L-rhamnose). The main transfer products to lactose, maltose, and sucrose as acceptors were identified as O-alpha-D-galactosyl-(1,6)-O-beta-D-galactosyl-(1,4)-D-glucose, O-alpha-D-galactosyl-(1,6)-O-alpha-D-glucosyl-(1,4)-D-glucose, and O-alpha-D-galactosyl-(1,6)-O-alpha-D-glucosyl-(1,2)-beta-D-fructoside (raffinose), respectively.

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Pseudomonas fluorescens H-601, isolated from soil, produces a-galactosidase.The enzyme was purified to homogeneity by disc electrophoresis after column chromatographies on Butyl-Toyopearl 650M, DEAE-Toyopearl 650M, and Toyopearl HW-55F. The enzyme had a molecular weight of 390,000 by gel filtration with Toyopearl HW-55F and 86,000 by SDS-polyacrylamide gel electrophoresis, and an isoelectric point of 6.3. The enzyme was most active at pH 6.0-7.0 and at 45°C and stable up to 40°C at pH 6.5 for 15min of incubation. The enzyme hydrolyzed PNP a-galactoside, ONPa-galactoside, melibiose, raffinose, and stachyose at the relative velocities of 100, 59, 28, 13, and 12. The enzyme had strong transfer activity and wide acceptor specificity.The a-galactosidase (a-D-galactoside galactohydrolase, EC 3.2.1.22) are a group of exo-type carbohydrases, which release agalactose from the non-reducing end side of the substrates such as synthetic a-galactosides and oligosaccharides having a-galactosidic bonds. The enzyme also catalyzes transgalactosylation as well as having hydrolysis action.1>2) a-Galactosidase has been used to remove raffinose and stachyose in soymilk processing and raffinose in sugar beet molasses by its hydrolytic action.3'4) Recently, oligosaccharides having a-galactosidic bonds such as raffinose and stachyose have attracted attention as strong bifldus growth factors. However, no study has been done on the synthesis of those oligosaccharides with the transgalactosylation of a-galactosidase. We have been working on the synthesis of various oligosaccharides and glycosides using transglycosylation of microbial enzymes such as cyclomaltodextrin glucanotransferase,5'6) amylomaltase,7) debranching enzyme,8) /?-