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β-(1 → 2)-Glucans can be synthesized by 1,2-β-oligoglucan phosphorylase using β-(1 → 2)-glucooligosaccharides as acceptors and α- d -glucose 1-phosphate as a donor. Using phosphorolysis of sucrose as a source of α- d -glucose 1-phosphate, we generated β-(1 → 2)-glucans with degrees of polymerization (DPs) up to approximately 280. Average DPs up to approximately 1000 were obtained using β-(1 → 2)-glucan with average DP of 160 as an acceptor and pure α- d -glucose 1-phosphate as a donor. A colorimetric assay of the β-glucosidase activity against the β-(1 → 2)-glucan products was used to determine their DPs. [Display omitted] • β-(1→2)-Glucan with a degree of polymerization of 280 was synthesized using sucrose. • A degree of polymerization of 1000 was achieved by avoiding use of sucrose as a donor. • Degrees of polymerization were evaluated using a colorimetric β-glucosidase assay. [ABSTRACT FROM AUTHOR]

Abstract A colorimetric determination method measuring the reducing ends of sugars is usually used for quantitative evaluation of polysaccharide-degrading activity of endo -type enzymes. However, no appropriate colorimetric method has been established for enzymatic assay of β-1,2-glucanases, which produce β-1,2-glucooligosaccharides from β-1,2-glucans. The Anthon-MBTH method has been potentially the most adaptable for color development of β-1,2-glucooligosaccharides among various known colorimetric methods for detecting the reducing power of oligosaccharides, since the difference between sophorose and other β-1,2-glucooligosaccharides in absorbance is relatively small. Almost the same color development was obtained for β-1,2-glucooligosaccharides when the heating time with the Anthon-MBTH method was changed. The kind of base and concentration of dithiothreitol did not markedly affect the color development. Most buffer components, salts and a chelating reagent used for usual enzymatic experiments did not inhibit color development. Furthermore, assay was performed successfully for a β-1,2-glucanase using the modified MBTH method. Highlights • β-1.2-Glucooligosaccharides were colored by the Anthon-MBTH method to similar extent. • We modified the Anthon-MBTH method for quantification of β-1.2-glucooligosaccharides. • The modified MBTH method was applied to assay of β-1.2-glucanase activity. [ABSTRACT FROM AUTHOR]