Impaired degradation of keratan sulfate in GM1-gangliosidosis

We have prepared a new radiolabeled substrate (galactose-N-acetylglucosamine 6-sulfate-1-³H]galactitol), from shark cartilage keratan sulfate, for an assay of acid β-galactosidase activity. Using this substrate, we found that there was a striking deficiency of β-galactosidase activity in the cultured skin fibroblasts of patients with GM₁-gangliosidosis. However, there seemed to be no quantitative differences in residual enzyme activity between type 1 and type 2 GM₁-gangliosidosis.