Reducing-end labelling

In these a-amylase reactions, glucose is not the primary product. Glucose is formed as a secondary product in the hydrolysis of maltotriose, maltotetraose and branched dextrins. Using 14C-reducing end labeled maltodextrins, G3 to G8, Robyt and French19 showed that porcine pancreatic a-amylase has different specificities for hydrolyzing the different linkages of the maltodextrins. The different frequencies for... 

A) Bond-cleavage frequencies measured from reducing-end labelled maltoheptaose... 

Scheme 6 Two-one binding in the degradation of maltotriose. O—O—ft, reducing-end labelled maltotriose u, subsite on the enzyme corresponding to a gluco-pyranoside unit binding position bond cleavages site. This mechanism is an integral...

Figure 3. Synthesis of reducing-end labeled maltodextrins by reaction of B. macerans cyclodextrin glucanosyl transferase with cyclomaltohexaose and various kinds of acceptors. Symbols are the same as in Figure 2.

Figure 4. Synthesis of (A) reducing-end labeled isomalto-dextrins by reaction of dextransucrase with nonlabeled sucrose and labeled sucrose and labeled a-methyl-D-glucopyranoside synthesis of (B) nonreducing-end isomaltodextrins by reaction with labeled sucrose and nonlabeled isomaltose and synthesis of (C) dual labeled isomaltodextrins by reaction with labeled sucrose and reducing-end labeled isomaltose. The circle represents a glucopyranosyl unit and a circle with a slash represents a reducing glucopyranose unit a triangle represents the fructose unit black are labeled and white are unlabeled.

Figure 6. Synthesis of variously labeled branched maltotetra-saccharides by reaction of dextransucrase with (A) nonlabeled sucrose and reducing-end labeled maltotriose, (B) labeled sucrose and reducing-end labeled maltotriose, and (C) labeled sucrose and nonlabeled maltotriose. Symbols are the same as in Figure 4.

Labeled maltosyl branched-cyclomaltodextrins can be synthesized by the action of isoamylase (19-20) or pullulanase (22,23) with various types of labeled maltose and cyclodextrin. Three types of labeled maltosyl cyclodextrins can be obtained (a) reducing-end labeled maltose attached to cyclodextrin (b) uniformly labeled maltose attached to cyclodextrin and (c) nonlabeled maltose attached to uniformly labeled cyclodextrin (Figure 8). 

Reducing end labelled maltooligosaccharides were synthesized by iucubating 50 (0. 5 mg) of C-glucose... 

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