Active
glycogen metabolism has been demonstrated in both normal and
glycogen-rich erythrocytes taken from patients with type III
glycogen storage disease. Activity of all
enzymes catalyzing the reactions required for the synthesis and degradation of
glycogen have been demonstrated in the mature erythrocytes. Uniformly labeled glucose-(14)C is incorporated into
glycogen in intact cells of both types during incubation. Replacement of the glucose-(14)C by unlabeled
glucose in the medium resulted in a significant loss of radioactivity from cellular
glycogen. In the absence of the substrate a progressive shortening of outer branches occurred during incubation of intact glucogen-rich cells. Using cells from patients with type III
glycogen storage disease, which have sufficient
glycogen content to be analyzed by beta-amylolysis, we demonstrated that the glucosyl units are first incorporated in the outer tiers, then transferred to the core where they tend to accumulate due to the absence of
amylo-1,6-glucosidase. The
glycogen-rich cells have a more rapid rate of
glucose utilization upon incubation which is not reflected by a higher
lactate production. The increased rate of
glucose utilization did not result from an increased rate of
glucose incorporation into
glycogen in affected cells. The rate of (14)CO(2) production from glucose-1-(14)C during incubation was not significantly different in the two types of cells unless
methylene blue was added as an electron acceptor, in which case the
glycogen-rich cells oxidized
glucose to CO(2) more rapidly.