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Glycogen and related polysaccharides inhibit the laforin dual-specificity protein phosphatase
- Source :
-
Biochemical & Biophysical Research Communications . Dec2004, Vol. 325 Issue 3, p726-730. 5p. - Publication Year :
- 2004
-
Abstract
- Abstract: Lafora disease, a progressive myoclonus epilepsy, is an autosomal recessive disease caused in ∼80% of cases by mutation of the EPM2A gene, which encodes a dual specificity protein phosphatase called laforin. In addition to its phosphatase domain, laforin contains an N-terminal carbohydrate-binding domain (CBD). Mouse laforin was expressed as an N-terminally polyHis tagged protein in Escherichia coli and purified close to homogeneity. The enzyme was active towards p-nitrophenylphosphate (50–80mmol/min/mg, Km 4.5mM) with maximal activity at pH 4.5. Laforin binds to glycogen, as previously shown, and caused potent inhibition, half maximally at ∼1μg/ml. Less branched glucose polymers, amylopectin and amylose, were even more potent, with half maximal inhibition at 10 and 100ng/ml, respectively. With all polysaccharides, however, inhibition was incomplete and laforin retained 20–30% of its native activity at high polysaccharide concentrations. Glucose and short oligosaccharides did not affect activity. Substitution of Trp32 in the CBD by Gly, a mutation found in a patient, caused only a 30% decrease in laforin activity but abolished binding to and inhibition by glycogen, indicating that impaired glycogen binding is sufficient to cause Lafora disease. [Copyright &y& Elsevier]
- Subjects :
- *GLUCOSE
*SUCROSE
*ESCHERICHIA coli
*ESCHERICHIA
Subjects
Details
- Language :
- English
- ISSN :
- 0006291X
- Volume :
- 325
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Biochemical & Biophysical Research Communications
- Publication Type :
- Academic Journal
- Accession number :
- 15424130
- Full Text :
- https://doi.org/10.1016/j.bbrc.2004.10.083