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An oligosaccharide has both a reducing and a non-reducing end. The reducing end of an oligosaccharide is the monosaccharide residue with hemiacetal functionality, thereby capable of reducing the Tollens’ reagent, while the non-reducing end is the monosaccharide residue in acetal form, thus incapable of reducing the Tollens’ reagent. [2]
It is a reducing sugar with only one reducing end, no matter how large the glycogen molecule is or how many branches it has (note, however, that the unique reducing end is usually covalently linked to glycogenin and will therefore not be reducing). Each branch ends in a nonreducing sugar residue.
The β(1→4) linkage at the non-reducing end of lacto-N-neotetraose makes it a type II chain. Through chemical and structural characterization, it has been identified that related oligosaccharides are often modifications of a single disaccharide. This has been observed for human milk oligosaccharides, with lactose as the common sugar, and in ...
These can be visualized using mass spectrometry. The oligosaccharides found on the A, B, and H antigen occur on the non-reducing ends of the oligosaccharide. The H antigen (which indicates an O blood type) serves as a precursor for the A and B antigen. [7]
For example, milk sugar (lactose) is a disaccharide made by condensation of one molecule of each of the monosaccharides glucose and galactose, whereas the disaccharide sucrose in sugar cane and sugar beet, is a condensation product of glucose and fructose. Maltose, another common disaccharide, is condensed from two glucose molecules. [7]
Working from the non-reducing end, β-amylase catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units at a time. During the ripening of fruit, β-amylase breaks starch into maltose, resulting in the sweet flavor of ripe fruit. They belong to glycoside hydrolase family 14.
The specific nature of this enzyme means that this chain of 7 carbons is usually attached to a glucose molecule that is in position three from the non-reducing end of another chain. Because the enzyme works with such specificity regarding the number of glucose units transferred and the position to which they are transferred, the enzyme creates ...
The open-chain form can be turned into a ring of carbon atoms bridged by an oxygen atom created from the carbonyl group of one end and the hydroxyl group of another. The cyclic molecule has a hemiacetal or hemiketal group, depending on whether the linear form was an aldose or a ketose. [38] In these cyclic forms, the ring usually has 5 or 6 atoms.