Amylopectin

Amylopectin is a highly branched polymer of glucose found in plants. It is one of the two components of starch, the other being amylose. Glucose units are linked in a linear way with &alpha(1→4) bonds. Branching takes place with &alpha(1→6) bonds occurring each 24 to 30 glucose units. Its counterpart in animals is glycogen which has the same composition and structure except for branching that occurs each 8 to 12 glucose units.

Amylopectin is formed by non-random a-1→6 branching of the amylose-type a-(1→4)-D-glucose structure. This branching is determined by branching enzymes that leave each chain with up to 30 glucose residues. Each amylopectin molecule contains a million or so residues, about 5% of which form the branch points. There are usually slightly more 'outer' unbranched chains (called A-chains) than 'inner' branched chains (called B-chains). There is only one chain (called the C-chain) containing the single reducing group.

Amylopectin interferes with the interaction between amylose chains (and retrogradation) and its solution can lead to an initial loss in viscosity and followed by a more slimy consistency.

Amylopectin is also a glucan with alpha(1-4) residues on the main chain. It contains branches linked alpha(1-6), and occur about once every 12-25 residues along the chain. The branch chains are typically 20-25 residues long. Hydrolysis of the chains into fragments yields maltose, usually done by enzymes such as alpha-amylase.

Amylopectin together with amylose compose starch, the primary storage polysaccharides of plants. Amylopectin is a polymer of glucose. It differs from amylose and resembles the animal storage polysaccharide, glycogen, in containing 1,6 branches in addition to 1,4 links between glucose units. Amylopectin is less branched, however, than glycogen, having branches approximately every 10-20 residues, versus every 8 residues in glycogen. Amylose, amylopectin, and glycogen all differ from the polysaccharide, cellulose, in containing exclusively 1,4 bonds in contrast to the 1,4 bonds of cellulose.

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