Maltose metabolism in serum free CHO culture involves lysosomal acid α-glucosidase

Mammalian cells have been previously shown to utilize maltose as an energy source for long-term cell growth. To characterize maltose uptake and consumption in CHO-K1, we measured its intracellular concentrations over time and tracked the incorporation of C13-labelled disaccharides into TCA cycle intermediates. Lysosomal acid α-glucosidase (GAA) was identified to potentially be involved in the initial reaction of breaking the α(1 → 4)-glycosidic bond in maltose, releasing two glucose residues for energy metabolism. Using a GAA-KO CHO-K1 cell line, we showed that GAA is involved in CHO-K1 maltose metabolism. Transport of maltose in wild-type and GAA-KO CHO-K1 is concentration-dependent. The rate of maltose uptake for GAA-KO cells was also linear when extracellular maltose is between 0 to 40 g/L, and saturation in uptake kinetics was not observed over that concentration range.