Amylopectin, synthesis

These studies, using Chlamydomonas mutants, provide evidence for the involvement of the GBSS, not only in amylose, but also in amylopectin synthesis, and suggest that a function for SSSII is in the synthesis of the intermediate size B-branch chains in amylopectin. 

It was proposed that maturation or trimming of the precursor of amylopectin, preamylopectin , was required in order for the amylopectin to aggregate into an insoluble granule structure. An alternative proposal is that during amylopectin synthesis there is a competition between polysaccharide aggregation into... 

Amylopectin synthesis involves chain elongation followed by branching. Branching occurs in clusters. Twenty to twenty-five chains may be included in a cluster, which is called the crystalline lamellae. About 80%-90% of the chains are involved in clusters [39]. Some of the chains in a cluster may exist as left-handed double stranded helices, which increase the stability of the clusters. Clusters are linked by long B-chains. Most B-chains extend into two to three clusters [39]. Between the clusters is a region with few branches. This region is called the amorphous lamellae. Thus, there is an alternating sequence of crystalline and amorphous lamellae within the amylopectin molecule. 

E. J. Hehre and D. M. Hamilton, Bacterial synthesis of an amylopectin-like polysaccharide from sucrose, J. Biol. Chem., 166 (1946) 77-78. 

These synthetic linear and branched molecules may be important as type polymers, particularly if the interconversion of amylose to amylopectin is intramolecular, in which case the initial molecular weight and molecular-weight distribution would be retained. There is the possibility that the in vitro synthesis may even result in a truly three-dimensional structure, as distinct from that of the natural component. 

Recently, the in vitro synthesis of amylopectin- or glycogen-like structures via a tandem reaction of phosphorylase and branching enzyme was reported [197-201]. 

This ehapter eonsiders the reeent view on moleeular structures of the amylose and amylopectin components in potato and how they are organized to form characteristie structures inside the stareh granules. The phosphorylation of starch, and the synthesis of its eomponents in normal and genetieally modified potatoes, is also discussed. 

Engelsen, S. B., Madsen, M. A. O., Blennow, A., Motawia, S., Moller, B. L., Larsen, S. (2003). The phosphorylation site in double helical amylopectin as investigated by a combined approach using chemical synthesis, crystallography and molecular modeling. FEES Lett, 541, 137-144. 

Review of the role of ADP-glucose pyrophosphorylase in the synthesis of amylose and amylopectin in starch granules. 

Efforts in genomics have also been directed at manipulation of starch synthesis to modify the amylose amylopectin ratio to increase susceptibility to a-amylase digestion (Smallwood, 2006), in this case to improve ethanol production via fermentation. Such developments would also have spin-offs for other industrial uses of starch where there is a preference for amylose or amylopectin forms. 

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