Structural Analysis by Enzymic Methods

Glycogens are attacked by three known groups of enzymes amylases and phosphorylases degrade a-D-(l 4)-linkages, whilst a-D-(l 6) inter-chain linkages are hydrolyzed by debranching enzymes. - 

Phosphorylases, in the presence of inorganic phosphate, remove D-glucose residues from the exterior chains of glycogen, according to the equation 

The action patterns of the above enzymes were determined by using the starch components as substrates with certain reservations, these enzymes may be used for studying the fine structure of glycogen. 

In the method of Cori and Lamer, glycogen (or amylopectin) is completely digested by the concurrent action of muscle phosphorylase and amylo-(l 6)-glucosidase. n-Glucose (which arises only from residues attached to C6 of an adjacent residue) and n-glucosyl phosphate (which is obtained from all other residues) are determined, and the branch-point content is calculated from the proportion of D-glucose. Only 10-15 mg. of glycogen is required for each assay the method has been applied to more 

Whelan and Roberts have devised an alternative method involving the successive action of salivary a-amylase and R-enzyme on glycogen. -By determining the number of reducing groups produced by action of R-enzyme on the a-dextrins, the proportion of (1 6) linkages can be calcu- 

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