Amylose amylopectin-type polysaccharide

Inasmuch as the polysaccharide is branched, it must be assumed that another enzyme is present, which in collaboration with the amylosucrase synthesizes a branched structure. This assumption is confirmed by the observation that the N. perflami preparations have the ability to convert amylose to an amylopectin-type polysaccharide without the production of reducing sugars. The cell-free enzyme preparation catalyzes the reaction involving the substitution of chiefly 1,4-linkages in the polysaccharide chain for the 1,2-linkage in sucrose ... 

Some natural polysaccharides are homopolysaccharides and they consist of a unique monomeric unit interconnected by identical links. Among these are cellulose, amylose, amylopectin, chitin, and glycogen, which are very common in nature. Polysaccharides can be formed from pentoses or hexoses with different types of ether links. Table 7.1.5 shows the type of links in some natural homopolysaccharides. However, many natural polysaccharides are formed from two or more types of residues and they are heteropolysaccharides. 

Amylosucrase 173) from Neisseria perflava utilizes sucrose for the synthesis of polysaccharides with properties intermediate between those of glycogen and amylopectin 174). Apparently, there are two enzymes responsible for this synthesis one enzyme converts sucrose into an amylose-type polysaccharide and the other enzyme, which is of the Q-enzyme type, breaks the straight chains to produce highly branched molecules. The resultant branched polysaccharides have about 12 D-glucose units for each nonreducing end unit. 

A polysaccharide is a polymer of many monosaccharides joined together. Four biologically important polysaccharides—amylose, amylopectin, glycogen, and cellulose— are all polymers of o-glucose that differ only in the type of glycosidic bonds and the amount of branching in the molecule. 

Storage polysaccharides of Prochloron isolated from Lis-soclinum pateUa are similar to the varieties of starch fotmd in the algae and terrestrial plants that is, the simultaneous presence of a nonramified and relatively short polymer of amylose type and a longer and strongly ramified polymer of amylopectin type (Fredrick, 1980). 

Molecular Structure. Most starches consist of a mixture of two polysaccharide types amylose, an essentially linear polymer, and amylopectin, a highly branched polymer. The relative amounts of these starch fractions in a particular starch are a major factor in determining the properties of that starch. 

Starch granules are composed of two types of a-glucan, amylose and amylopectin, which represent approximately 98-99% of the dry weight. The ratio of the two polysaccharides varies according to the botanical origin of the starch. 

Most potato starches are composed of a mixture of two polysaccharides, a linear fraction, amylose, and a highly branched fraction, amylopectin. The content of amylose is between 15 and 25% for most starches. The ratio of amylose to amylopectin varies from one starch to another. The two polysaccharides are homoglucans with only two types of chain linkage, a-(l 4) in the main chain and a-(l 6)-linked branch chains. Physicochemical properties of potato and its starch are believed to be influenced by amylose and amylopectin content, molecular weight, and molecular weight distribution, chain length and its distribution, and phosphorus content (Jane and Chen, 1992). 

The starch granule contains two polysaccharide types amylose, which is a linear polymer, and amylopectin, which is a branched polymer. Amylose is composed of linear chains of about 800 to 22,000 a-D-glucopyranosyl units in (a-1,4) linkage... 

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