Defective EPM2A does not dephosphorylate phosphoglycogen (type 2A disease)

Stable Identifier
Reaction [transition]
Homo sapiens
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EPM2A (laforin) associated with cytosolic liver- and muscle-form glycogen granules normally catalyzes the hydrolytic removal of the small numbers of phosphate groups incorporated into glycogen (Minassian et al. 1998, Serratosa et al. 1999, Tagliabracci et al. 2011). Defects in EMP2A (laforin) are the cause of the commonest form of Lafora disease. The three missense mutant forms of EPM2A (laforin) annotated here are examples of the disease-associated EPM2A alleles that have been described (Fernandez-Sanchez et al. 2003).
Literature References
PubMed ID Title Journal Year
9931343 A novel protein tyrosine phosphatase gene is mutated in progressive myoclonus epilepsy of the Lafora type (EPM2)

Michelucci, R, Gallardo, ME, de Córdoba, SR, Tassinari, CA, Dravet, C, Malafosse, A, Augustijn, PB, Gómez-Garre, P, Berkovic, SF, Lindhout, D, de Bernabé, DB, Serratosa, JM, Grid, D, Anta, B, Topcu, M

Hum. Mol. Genet. 1999
21356517 Phosphate incorporation during glycogen synthesis and Lafora disease

Ishihara, M, Hurley, TD, Glushka, J, Heiss, C, Karthik, C, Roach, PJ, Contreras, CJ, Tagliabracci, VS, DePaoli-Roach, AA, Azadi, P

Cell Metab. 2011
9771710 Mutations in a gene encoding a novel protein tyrosine phosphatase cause progressive myoclonus epilepsy

Jardim, L, Snead, OC, Soder, S, Lee, JR, Dunham, I, Huizenga, J, Delgado-Escueta, AV, Mungall, AJ, Satishchandra, P, Tsui, LC, Gardner, R, Scherer, SW, Andermann, E, Rouleau, GA, Lopes-Cendes, I, Herbrick, JA, Carpenter, S, Fong, CY, Minassian, BA

Nat. Genet. 1998
14532330 Laforin, the dual-phosphatase responsible for Lafora disease, interacts with R5 (PTG), a regulatory subunit of protein phosphatase-1 that enhances glycogen accumulation

Heath, KE, Rodríguez de Córdoba, S, Fernández-Sánchez, ME, Gómez-Garre, P, Medraño-Fernández, I, Criado-García, O, García-Fojeda, B, Serratosa, JM, Sanz, P

Hum. Mol. Genet. 2003
Catalyst Activity

carbohydrate phosphatase activity of mutant EPM2A:PPP1R3C:phosphoglycogen-GYG1:GYS1-a tetramer [cytosol]

Normal reaction
Functional status

Loss of function of mutant EPM2A:PPP1R3C:phosphoglycogen-GYG1:GYS1-a tetramer [cytosol]

Name Identifier Synonyms
glycogen storage disease DOID:2747 glycogenosis
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