An enzymatically produced novel cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->} (cyclic maltosyl-(1-->6)-maltose), from starch

A bacterial strain M6, isolated from soil and identified as Arthrobacter globiformis, produced a novel nonreducing oligosaccharide. The nonreducing oligosaccharide was produced from starch using a culture supernatant of the strain as enzyme preparation. The oligosaccharide was purified as a crystal preparation after alkaline treatment and deionization of the reaction mixture. The structure of the oligosaccharide was determined by methylation analysis, mass spectrometry, and (1)H and (13)C NMR spectroscopy, and it was demonstrated that the oligosaccharide had a cyclic structure consisting of four glucose residues joined by alternate alpha-(1-->4)- and alpha-(1-->6)-linkages. The cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->}, was found to be a novel oligosaccharide, and was tentatively called cyclic maltosyl-maltose (CMM). CMM was not hydrolyzed by various amylases, such as alpha-amylase, beta-amylase, glucoamylase, isoamylase, pullulanase, maltogenic alpha-amylase, and alpha-glucosidase, but hydrolyzed by isomalto-dextranase to give rise to isomaltose. This is the first report of the cyclic tetrasaccharide, which has alternate alpha-(1-->4)- and alpha-(1-->6)-glucosidic linkages.