Structure of a Low Molecular Weight Form of Glycogem Isolated from the Liver in a Case of Glycogen Storage Disease*

An incompletely branched, low molecular weight form of glycogen has been isolated from liver tissue of a patient with glycogen storage disease. Digestion with pullulanase and @-amylase, oxidation by periodate, Smith degradation, spectral studies of the iodine complexes, osmotic pressure measurements, and end group analysis gave results which indicate a molecular weight range of 8,000 to 15,000 with an average chain length of 17 to 18 glucose units per branch point. The substance was found in heart and kidney tissues in addition to liver. In an attempt to evaluate the role of branching enzyme in the disease, it was found that the branching enzyme was not stable in normal frozen liver and disappeared with a half-life of about 5 weeks. Clinical, chemical, and pathological factors in this case were similar to those previously reported in the case of glycogen storage disease type IV.