Alpha-1,4 glycosidic bonds

The molecular characterisation of the neoamylose by C-NMR revealed a 1,4-coupling of the anhydroglucose units via the alpha glycosidic bond in a strictly linear manner and a chain length of degree of polymerisation 60-100 glucose units... 

Starch (Figure 12.20) is a polymer of glucose that we can digest. Starch is poly [l<->4] a-glucose. The glycoside bonds in starch are alpha. This configuration puts a bend in the chain. In fact, starch adopts a helical conformation. 

Quirasco M, Lopez-Munguia A, Pelenc V, Remaud M, Paul F, Monsan P (1995) Enzymatic production of glucooligosaccharides containing alpha-(l,2) glycosidic bonds. Potential application in nutrition. Ann N Y Acad Sci 750 317-320... 

The mechanism of action is probably like that proposed for pancreatic alpha-amylase, which involves protonation of the glycosidic bond by an imidazolium ion of the enzyme, followed by an attack on the anomeric carbon atom by a C02 group of the enzyme, resulting in a glycosyl ester (/3 form of the D-glucose residue) which is then hydrolyzed by attack by water at the anomeric carbon atom.9... 

B. a linear polymer of glucose units linked by alpha(l-4) glycosidic bonds... 

In polyuronides the glycosidic bond may be attached to any of the carbons 2 to 6. The ease of hydrolysis of these compounds may be influenced by variation in the point of attachment. Alpha glycosidic linkages seem to be more easily ruptured than beta linkages. 

At the request of the Codex Committee on Food Additives and Contaminants at its thirty-eighth session (Codex Alimentarius Commission, 2006), the Committee evaluated the enzyme isoamylase (glycogen a-1,6-glucanohydrolase EC 3.2.1.68). Isoamylase catalyses the hydrolysis of 1,6-a-D-glucosidic branch linkages in glycogen, amylopectin and their beta-limit dextrine. It has no or only limited activity on linear polysaccharides linked by a-1,6-glycosidic bonds (e.g. pullulan) and on alpha-limit dextrine. 

The biogenesis of cyanogenic glycosides, which have the cyano group alpha to the glycosyl bond, was established. It starts from a-amino acid as follows [29] ... 

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