Branching in glycogens

Debranching enzyme deconstructs the branches in glycogen that have been exposed by glycogen phosphorylase. The two-step process by which this occurs is diagrammed in Figure 1-14-4. Debranching enzyme ... 

Proof of the presence of multiple branching in glycogens and amylo-pectin comes from an examination of the limit dextrins produced by the... 

Patients with Cori s disease lack the debranching enzyme, and therefore the structure of liver and muscle glycogen is unusual, with short outer branches. Design an assay that would enable you to demonstrate the presence of short branches in glycogen from one of these patients. Also explain how you would demonstrate that the debranching enzyme is deficient in these patients. 

G. C. Gibbons and R. A. Boissonnas, Starch. XLVIII. The position of branching in glycogen and amylopectin, Helv. Chim. Acta, 33 (1950) 1477-1481. 

Glycogen is the main storage polysaccharide of animal cells. Like amylopectin, glycogen is a polymer of (a 1—>4)-linked subunits of glucose, with (a 1 >6)-linked branches, but glycogen is more extensively branched (on average, every 8 to 12 residues) and more compact than starch. Glycogen is especially abundant in the liver,... 

X-ray diffraction studies support the double-helical structure but suggest a parallel orientation of the amylose chains.81 Since amylose has not been obtained as single crystals the diffraction data do not give a definitive answer. However, if double helices are formed by adjacent branches in amylopectin and glycogen the two strands would be parallel. Starch granules also contain amorphous starch which appears to contain single helices, possibly wrapped around lipid materials.82... 

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