グリコシダーゼ類の基質特異性における柔軟性 : 非天然型オリゴ糖,配糖体合成への利用の可能性 Flexibility of Glycosidases in Substrate Specificity : Their Possible Application to the Synthesis of Unusual Oligosaccharides and Glycosides
Specificities of glycosidases were studied from the viewpoint of the synthesis of oligosaccharides and glycosides that are not naturally occurring. Trehalase from Lobosphaera sp. catalyzed conden-sation not only of glucose (Glc) but also of 2-deoxy glucose (dGlc), yielding trehalose and dideoxy-trehalose, respectively. Deoxy-trehalose was also synthesized in a mixture of Glc and dGlc. Activi-ties for trehalose derivatives decreased considerably because of their deoxy site. Glucoamylases from Aspergillus niger and Rhizopus niveus, and α-glucosidase from A. niger afforded deoxy-oli-gosaccharides by the condensation of dGlc, while α-glucosidases from Torula and Saccharomyces gave them in low yields. Deoxy-glucobioses with α-1, 3-, 1, 4- and 1, 6-linkages were identified as the products of glucoamylase and α-glucosidase. The hydrolysis rates of these glucobioses and the transfer action of α-glucosidase seemed to affect the product composition, especially in the early stage of the reactions, and afterwards, the 1, 6-linked saccharide accumulated predominately. Strains of Clavibacter michiganense and Flavobacterium johnsonae produced novel β-glucosidases that hydrolyzed the β-glucosyl ester linkage of steviol glycosides. Transglucosylation occurred when this linkage was degraded, ρ-Hydroxybenzoyl glucose was chemically synthesized as a substrate containing the β-glucosyl ester linkage. Several β-glucosidases, such as that from Caldocellum saccharolyticum, hydrolyzed the substrate. ρ-Hydroxybenzoyl galactose with the β-galactosyl ester linkage was also synthesized, and was examined as a substrate for β-galactosidases. The activities showed great diversity depending on the enzyme origin. The enzyme from Penicillium multicolor showed the highest activity among those tested. β-Galactosidases catalyzed galactosylation not only of a hydroxyl group but also of a thiol group in the condensation of galactose and 2-mercap-toethanol. The enzymes from <I>A</I>. oryzae and <I>P</I>. multicolor were effective for the synthesis of thio-galactoside. The usual galactoside was synthesized more rapidly than the thin-galactoside, although the latter accumulated predominately as the reaction proceeded.
- 応用糖質科学 : oyo toshitsu kagaku = Journal of applied glycoscience
応用糖質科学 : oyo toshitsu kagaku = Journal of applied glycoscience 47(2), 261-267, 2000-06-30