Glycogen metabolism in human skin fibroblasts. Influence of maltose on the activity of acid alpha-1, 4-glucosidase.

Maltose added to medium in a concentration of 100 mg/100 ml enhances the hydrolytic activity of acid alpha-1, 4-glucosidase in skin fibroblasts in culture derived from normal human subjects, but under the same conditions maltose has no demostrable effect on the enzyme in fibroblasts derived from skin of patients with Cori Type II glycogenosis. Upon addition of maltose to Cori Type II fibroblasts there is a marked decrease of glucose in medium overlying the cells with a concomitant marked increase in glycogen content of the same cells. Glycogen decreases in a similar manner in both normal and mutant cell types after 16 days in culture. This apparent utilization or degradation of glycogen in Cori Type II fibroblasts in culture is difficult to explain unless only a proportion of the polysaccharide accumulates within lysosomes. We propose, therefore, that extra-lysosomal glycogen which accumulates in fibroblasts from Cori Type II glycogenosis may be more easily degraded by glycogenolytic cytoplasmic enzymes, particularly in cells grown for as long as 2 wk in glucose-starved media.