糖水酸基がα-グリコシダーゼとリパーゼの活性と特異性に及ぼす影響について

抄録

Using possible monodeoxy derivatives of p-nitrophenyl (pNP) α-D-glucopyranoside, -mannopyranoside, and -galactopyranoside as probe substrate, glycon specificities of α-glucosidases, -mannosidases, and -galactosidases from various sources were investigated, through hydrolysis of them. α-Glucosidases of Saccharomyces cerevisiae, Bacillus stearothermophilus, and honeybee hydrolyzed no deoxy derivatives, while the enzymes of rice, sugar beet, flint corn, and Aspergillus (A.) niger hydrolyzed the 2-deoxy derivative with substantially high activities. Moreover, flint corn and A. niger enzymes showed, although low, activities against the 3-deoxy derivative. Jack bean and almond α-mannosidases both showed sufficient activities toward 6-deoxy derivative. A. niger α-galactosidase acted on only 2-deoxy derivative with substantially high activity, while the enzymes of green coffee bean and Mortierella vinacea hydrolyzed not only the 2-deoxy derivative but also 6-deoxy one with low activities. Oligosaccharides that contain 2- or 3-deoxygenated glucose were synthesized by the transesterification reaction of A. niger α-glucosidase. α- and β-Anomers of methyl 6-ο-(p-tolylsulfonyl)-D-glucopyranoside, -mannopyranoside, and -galactopyranoside were acetylated partially by lipase-catalyzed transesterification with vinyl acetate. A lipase from Pseudomonas cepacia (lipase PS) reveaed high activity and regioselectivity for the esterification of them.α-Glycopyranosides were acetylated preferentially at the C-2 hydroxyl group, while corresponding β-anomers were acetylated preferentially at the C-3 hydroxyl group. The best selectivity was observed in the reaction of the glucopyranosides. Using methyl 3-ο -acetyl-6-ο -(p-tolylsulfonyl)-β-Dglucopyranoside, which was prepared in quantitative yield by the lipase PS-catalyzed regioselective acetylation, as a common starting material, highly deoxygenated monosaccharides, namely 2, 6-dideoxy-D-arabino-hexopyranose, 2, 4-dideoxy-D-threo-hexopyranose, and 2, 4, 6-trideoxy-D-threo-hexopyranose, respectively, were chemically synthesized in good yields.