GAA hydrolyzes lysosomal glycogen

Stable Identifier
Reaction [transition]
Homo sapiens
GAA hydrolyzes alpha(1,6) linkages in lysosomal glycogen, GAA hydrolyzes alpha(1,4) linkages in lysosomal glycogen
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While most glycogen is cytosolic, glycogen granules are also found in lysosomes, which they are thought to enter by autophagy. Once in lysosomes, the polysaccharide component of the granules is degraded by a single enzyme, lysosomal alpha-glucosidase (GAA), which hydrolyzes both alpha(1,4) and alpha(1,6) linkages to yield free glucose (Brown et al. 1970). The fate of the glycogenin protein component of the granules has not been studied; it is thought to be degraded by the diverse lysosomal proteases (Muller et al. 2012).
Mutations that reduce the activity of GAA are associated with glycogen storage disease type II (Pompe disease) (Hirschhorn & Reuser 2001; Leslie & Tinkle). The most active forms of GAA are 70 and 76 kDa polypeptides generated by removal of both aminoterminal and carboxyterminal fragments (Brown et al. 1970; Hoefsloot et al. 1988; Wisselaar et al. 1993).

Literature References
PubMed ID Title Journal Year
21767668 Specific functions of lysosomal proteases in endocytic and autophagic pathways

Dennemärker, J, Reinheckel, T, Müller, S

Biochim. Biophys. Acta 2012
8420990 Structural and functional changes of lysosomal acid alpha-glucosidase during intracellular transport and maturation

Kroos, MA, Reuser, AJ, van Beeumen, J, Hermans, MM, Wisselaar, HA

J. Biol. Chem. 1993
5264799 Simultaneous absence of alpha-1,4-glucosidase and alpha-1,6-glucosidase activities (pH 4) in tissues of children with type II glycogen storage disease

Brown, BI, Jeffrey, PL, Brown, DH

Biochemistry 1970
3049072 Primary structure and processing of lysosomal alpha-glucosidase; homology with the intestinal sucrase-isomaltase complex

Kroos, MA, Reuser, AJ, van Beeumen, J, Oostra, BA, Hoogeveen-Westerveld, M, Hoefsloot, LH

EMBO J. 1988
Catalyst Activity

alpha-glucosidase activity of GAA (70, 76 kDa) [lysosomal lumen]

Orthologous Events
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