| First Author | Wang W | Year | 2004 |
| Journal | Biochem Biophys Res Commun | Volume | 325 |
| Issue | 3 | Pages | 726-30 |
| PubMed ID | 15541350 | Mgi Jnum | J:93823 |
| Mgi Id | MGI:3505811 | Doi | 10.1016/j.bbrc.2004.10.083 |
| Citation | Wang W, et al. (2004) Glycogen and related polysaccharides inhibit the laforin dual-specificity protein phosphatase. Biochem Biophys Res Commun 325(3):726-30 |
| abstractText | Lafora disease, a progressive myoclonus epilepsy, is an autosomal recessive disease caused in approximately 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, K(m) 4.5mM) with maximal activity at pH 4.5. Laforin binds to glycogen, as previously shown, and caused potent inhibition, half maximally at approximately 1mug/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. |
