Oligosaccharides glucosidase

Figure 47-9. Schematic pathway of oligosaccharide processing. The reactions are catalyzed by the following enzymes , oligosaccharideiprotein transferase , a-glucosidase I ...

The protein-bound oligosaccharide is then partially processed by glucosidases and mannosidases if no additional sugars are added, this results in a high-mannose chain. 

Results of an experiment with an oligosaccharide free from amino acid were less conclusive, but were not incompatible with the structure shown. The oligosaccharide was prepared from a separated glycoprotein fraction having a D-mannose hexosamine ratio of 5 3. a-D-Mannosidase and 2-acetamido-2-deoxy-/3-D-glucosidase were used alternately. Initially, a-D-mannosidase removed about 1.5 D-mannose residues per molecule. Subsequent treatment of the residual oligosaccharide with 2-acetamido-2-deoxy-/3-D-glucosidase released rather less than one proportion of hexosamine residue, and then another 1.5 residues of D-mannose became open to attack by a-D-mannosidase. 

As regards the occurrence of /3-D-linked disaccharides in the absence of a /3-D-linked substrate, one is tempted to conclude that these oligosaccharides are synthesized by the enzymic reversion of D-glucose by a /3-D-glucosidase. As White and Maher100 have found that their honey-invertase preparation had no /3-D-glucosidase activity, it would appear that these sugars are carried into the hive as constituents of nectar. 

Oligo-( 1— 6)-D-glucosidase isomaltase, dextrin 6-a-D-glucanohydrolase hydrolysis of (1— -6)-a-D-glucosyl links in isomaltose, panose, and gluco-oligosaccharides produced from starch by alpha amylase... 

Fig. 3. —Proposed Structure of a Portion of theHemieellulosicXyloglucan of the Primary Cell-Wall of Dicots (After Albersheim5-64). [Heptasac-charide A and nonasaccharide B are derived from oligosaccharide C by the action of endo-(l—>4)-/ -D-glucanase at the bonds indicated by arrows. Pentasaccharide D is derived from "B by the combined action of a-L-fucosidase, a-D-xylosidase, and /J-D-glucosidase. A = L-arabinopyranose F = L-fucose G = D-glucose Gal = D-galactose X = D-xylose.]...

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