Essential for the degradation of glycogen in lysosomes (PubMed:1856189, PubMed:7717400, PubMed:14695532, PubMed:18429042). Has highest activity on alpha-1,4-linked glycosidic linkages, but can also hydrolyze alpha-1,6-linked glucans (PubMed:29061980). Hydrolysis of terminal, non-reducing (1->4)-linked alpha-D-glucose residues with release of alpha-D-glucose. The different forms of acid glucosidase are obtained by proteolytic processing. Phosphorylation of mannose residues ensures efficient transport of the enzyme to the lysosomes via the mannose 6-phosphate receptor. There are three common alleles of GAA: GAA*1, GAA*2 and GAA*4. The sequence shown is that of allele GAA*1, which is the most common. Alleles GAA*2 and GAA*4 are much rarer. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyl hydrolase 31 family. Mutations in alpha-glucosidase Alpha-glucosidase entry Leiden Open Variation Database (LOVD)