Species-specific differences in the processing of acid α-glucosidase are due to the amino acid identity at position 201.

Acid α-glucosidase (GAA) is a lysosomal enzyme that hydrolyzes glycogen to glucose. Deficiency of GAA causes Pompe disease. Mammalian GAA is synthesized as a precursor of ~110,000 Da that is N-glycosylated and targeted to the lysosome via the M6P receptors.