title: Hexosaminidase isozyme in type O Gm2 gangliosidosis (Sandhoff-Jatzkewitz disease).
abstract: The residual enzyme of the fibroblasts of a child with homozygous type 0 GM2 gangliosidosis (Sandhoff-Jatzkewitz disease) has been found to correspond with a minor fraction of enzyme which can be isolated from normal fibroblasts by repeated chromatography. This enzyme is designated as hexosaminidase (hex) S. It reacts with antiserum prepared against homogeneous hex A but not with serum prepared against homogeneous hex B. These findings support our previously described model of the relationship between hex A and hex G: hex A has the structure (alpha beta)3, while hex B is (beta)6. Type B GM2 gangliosidosis (Tay-Sachs disease) is the alpha- mutation, while type 0 GM2 gangliosidosis (Sandhoff-Jatzkewitz disease) is the beta- mutation. In the absence of normal beta subunits there is increased polymerization of alpha subunits forming hex S, which probably has a structure of (alpha)6. A parallel between the thalassemias and GM2 gangliosidosis is evident: deficiency of one of the chains of which the protein is composed leads to an excess of polymers comprised of the other chains. In type B GM2 gangliosidosis, the excess of beta chanis leads to increased amounts of hex B beta)6; in type 0 GM2 gangliosidosis, the excess of alpha chains leads to formation of increased amounts of the alpha chain polymer, hex S.
mesh_terms: D000941:Antigens / Q000032:analysis; D002845:Chromatography; D003241:Consanguinity; D005260:Female; D005347:Fibroblasts / Q000032:analysis; D005733:Gangliosidoses / Q000235:genetics*; D006596:Hexosaminidases / Q000032:analysis* / Q000276:immunology; D006801:Humans; D007223:Infant; D007527:Isoenzymes / Q000032:analysis*; D008970:Molecular Weight; D010375:Pedigree; D013577:Syndrome
chemical_list: D000941:Antigens; D007527:Isoenzymes; D006596:Hexosaminidases