Abstract
ABSTRACT: A case of infantile GM2 gangliosidosis with high residual/S-hexosaminidase A activity toward the synthetic substrate 4-methylumbelliferyl-2-acetamido-2- deoxy-/S-D-glucopyranoside was diagnosed prenatally. Extracts from cultured amniotic fluid cells of the fetus had a hexosaminidase A activity of 27% of total hexosaminidase but were almost completely unable to degrade [3H]ganglioside GM2 (less than 0.5% of control values) when assayed in the presence of the natural activator protein. These results were confirmed by analyses of fetal muscle fibroblasts, liver, and brain. All tissues examined showed a profound deficiency of ganglioside GM2 galactosaminidase despite hexosaminidase A levels in the heterozygote range. In brain tissue, ganglioside GM2 content was elevated more than 4-fold. Hydrolysis of p-nitrophenyl glucosaminide-6- sulfate, a substrate specific for hexosaminidases A and S, by tissue extracts was also markedly reduced but the residual activities found (5% in liver, 12% in fibroblasts, and 16% in brain) were much higher than those with the physiological lipid substrate, ganglioside GM2.
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Conzelmann, E., Nehrkorn, H., Kytzia, HJ. et al. Prenatal Diagnosis of GM2 Gangliosidosis with High Residual Hexosaminidase A Activity (Variant B1; Pseudo AB Variant). Pediatr Res 19, 1220–1224 (1985). https://doi.org/10.1203/00006450-198511000-00022
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DOI: https://doi.org/10.1203/00006450-198511000-00022