Mucolipidosis Types II and III are autosomal recessive disorders having many of the clinical features of the mucopolysaccharidosis but lacking the mucopolysacchariduria. Cultured fibroblasts from patients with either of these disorders are characterized by the presence of cytoplasmic inclusions and a generalized reduction in most intracellular lysosomal enzymes associated with a marked increase in the same enzymes in the extracellular fluid. We now wish to report that there is a 3 to 4 fold increase in bound sialic acid in fibroblasts cultured from patients with either of these disorders. Additionally, it is shown that mucolipidosis Type II fibroblasts lack acid sialidase activity (pH 4.2 in 0.05 M acetate buffer) while mucolipidosis III cells have reduced levels of the same enzyme. In contrast, normal fibroblasts, grown and assayed under identical conditions, are shown to have a sialidase capable of removing sialic acid from added fetuin at pH 4.2 in 0.05 M acetate buffer. It is speculated that the sialidase deficiency and the associated alterations in bound sialic acid may play a central role in a number of biochemical abnormalities noted previously in these disorders.
|Original language||English (US)|
|State||Published - Jan 1 1976|
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