Pathogenesis of Pompe's Disease

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We purified acid alpha-glucosidase from human placenta and pig liver. The purification procedures were followed essentially as described previously. Recently we found that the enzyme showed the heterogeneity in its affinity to Sephacryl s-200 gel. The enzyme was separated into two major components (S1 and S2). Each component was further separated into two (76 KDa and 67 KDa components) by SDS-PAGE and also chromatofocusing. The tissue distribution of these four components (76 KDa and 67 KDa of S1 and S2 components) was investigated. The liver, heart and kidney enzymes were consisted of these four components. However, the macrophage enzyme contained only S1 76 KDa component. The 4-methylumbelliferyl alpha-glucosidase activities of these four components were all inhibited competitively by glycogen, maltose, isomaltose and turanose, which suggests that the acid alpha-glucosidase has a single substrate binding site which is common to those substrates. According to the amino acid sequence a … More nalysis, the four components were considered to be the same gene product. Sugar chain analysis of these four components and CRM (immunologically cross-reactive material which reacts with anti acid alpha-glucosidase) from Pompe's disease was performed by the lectin-nitrocellulose sheet method. The S1 and S2 components and CRM contained the mannose. Con A staining patterns before and after digestion with Endo H, Endo F and PNGase indicated that there may be small amounts of other sugar chain different from mannose-rich N-linked chain. In addition, CRM from Pompe's disease contains small amounts of sialic acid in its sugar chains. These experiments were also carried out using Pompe's disease fibroblasts which were transfected with SV 40 large T DNA. cDNA and mRNA from Pompe's disease fibroblasts are now investigating.From a cytopathological view point, lysosomal storage disease may be classified into two groups : A and B. In the disease of A group, the storage substances are mainly observed in the parenchymal cells. In the Pompe's disease, large amounts of glycogen were stored in the hepatocytes and muscle. The acid alpha-glucosidase localized mainly in the parenchymal cells such as hepatocytes and muscle cells. On the other hand, in the diseases of group B, the storage substances were found in the macrophages as in the case of Hurler disease. We purified alpha-L-iduronidase from human placenta and pig liver. alpha-L-Iduronidase was demonstrated immunohistochemically in the macrophages. We are now investigating the lysosomal diseases, group A and B, pathologically, biochemically and genetically. Less