A-l,6 -Glycosidic linkages

Fig. 1. Stmctural diagram of (a) P-cyclodextrin and (b) two of the glucopyranose units illustrating details of the a-(l,4) glycosidic linkage, C-1 (d) chair...

The PGA salt of D AP has shown pharmacological results (peak timer shifted to a later time, increased Imax) corresponding to an increased contact time [12]. PGA consists of linear chains of D-galacturonic acid units (pyranose form), joined in a(l- 4)-glycosidic linkages, with a molecular weight ranging from 25 103 to 100 x 3. It formed a soluble salt or polyanionic complex with the... 

Amylose (linear starch) contains only a-l,4-glycosidic linkages involving the groups indicated by the arrows... 

The difference in structure between amylose and amyiopectin is important when selecting the appropriate starch substrate for amylase determinations (see Chapter 21). The rate of hydrolysis is affected by structural differences in the starch. a-Amylase from the pancreas hydrolyzes internal a-l,4 glycosidic linkages. This hydrolysis results initially in the production of some maltose and a mixture of dextrins, which are subsequently hydrolyzed to maltose. The -1,6-... 

Mobilization of glycogen stores also requires the participation of a debranching enzyme because phosphorylase ceases to cleave a-l,4-glycosidic linkages four glucosyl residues from an a-1,6-branch site. The debranching enzyme has two catalytic activities a transferase activity and a glucosidase... 

Both amylose, glycogen, and amylopectin possess polymers of glucose residues that are linked by a-l,4-glycosidic linkages. Glycogen and amylopecdn also possess branches that are connected to the a-l,4-linked chain by a-1,6-... 

In this reaction phosphorylase catalyzes the polymerization of glucose-1-phosphate in order to obtain linear polysaccharide chains with a-(l—>4) glycosidic linkages the glycogen branching enzyme is able to transfer short, a-(l—>4) linked, oligosaccharides from the nonreducing end of starch to an a-(l—>6)... 

Cellulose is the structural material of higher plants. Cotton, for example, is composed of about 90% cellulose, and wood is about 50% cellulose. Like amylose, cellulose is composed of unbranched chains of D-glucose units. Unlike amylose, however, the glucose units in cellulose are joined by S-l,4 -glycosidic linkages rather than by a-l,4 -glycosidic linkages. 

In addition to proteases, a limited number of brands employ amylases. Detergent amylases catalyze hydrolysis of the a-l,4-glycosidic linkages in starch. As such they show benefits on a number of common food sols like gravies, sauces, pastas, and baby foods. 

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