Biosynthesis of xyloglucan in suspension-cultured soybean cells. Occurrence and some properties of xyloglucan 4-beta-D-glucosyltransferase and 6-alpha-D-xylosyltransferase.
A particulate enzyme fraction that catalyzes the transfer of glucose from UDP-[14C]glucose and of xylose from UDP-[14C]xylose into a xyloglucan has been isolated from suspension-cultured soybean cells. The incorporation of radioactivity from [14C]xylose into the polysaccharide was dependent on the presence of UDP-glucose in the incubation mixture, and that from [14C]glucose was dependent on the concentration of UDP-xylose in the mixture. Mn2+ was required for the incorporation of xylose and the optimum concentration of Mn2+ was about 10 mM. This reaction showed a pH optimum at 6.5 to 7.0 in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer and was inhibited by phosphate buffer and Tris buffer. On hydrolysis with Trichoderma endoglucanase, the polysaccharide synthesized in vitro gave a pentasaccharide, a hepatasaccharide, and a small amount of non-asaccharide. Based on the results from fragmentation and methylation analyses, the following structures were proposed for the penta- and the heptasaccharides from the xyloglucan synthesized in vitro: (formula, see text).
D002236:Carbohydrate Conformation; D002478:Cells, Cultured; D005936:Glucans; D005964:Glucosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D010430:Pentosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D011134:Polysaccharides / Q000096:biosynthesis*; D013025:Glycine max; D014990:Xylans
D005936:Glucans; D011134:Polysaccharides; D014990:Xylans; C029353:xyloglucan; D005964:Glucosyltransferases; C032411:xyloglucan 4-beta-D-glucosyltransferase; D010430:Pentosyltransferases; C029368:xyloglucan xylosyltransferase