Arylsulfatases A and B in EBV-transformed lymphoid cell lines: studies on their molecular forms in cells from patients with inborn sulfatase deficiencies. Comparative diagnostic value of enzymatic assays.

The enzyme activity of arylsulfatase A and arylsulfatase B was studied in Epstein-Barr virus-transformed lymphoid cell lines established from control individuals and patients affected with metachromatic leukodystrophy, mucopolysaccharidosis type VI (or Maroteaux-Lamy syndrome) and multiple sulfatase deficiency. Lymphoid cells derived from patients with metachromatic leukodystrophy showed a severe deficiency in cerebroside sulfatase activity, as measured using radiolabelled sulfatide, but some residual activity of arylsulfatase A when measured with the chromogenic substrate, para-nitrocatechol sulfate. Lymphoid cells from mucopolysaccharidosis type VI had virtually no arylsulfatase B activity. In cells from patients with multiple sulfatase deficiency, the activities of lysosomal sulfatases as well as steroid sulfatase were deficient. Study of the molecular forms of arylsulfatases confirmed the complete deficiency of arylsulfatase A and arylsulfatase B activities in metachromatic leukodystrophy and mucopolysaccharidosis type VI lymphoid cells, respectively. The arylsulfatase A defect in metachromatic leukodys-lymphoid cells, respectively. The arylsulfatase A defect in metachromatic leukodystrophy cells could be demonstrated on focused fractions even using the artificial substrates, para-nitrocatechol sulfate and 4-methylumbelliferyl sulfate. To investigate the discrepancy of the arylsulfatase A activity data observed between whole cell homogenates and focused fractions when using the synthetic substrates, assays were tentatively performed for optimizing the determination of arylsulfatase A on crude homogenates of lymphoid cells. Although this work has indicated methodological limitations of the enzymatic assay of arylsulfatase A in lymphoid cells using methylumbelliferyl sulfate, it emphasizes the validity of lymphoid cell lines as an experimental model for the study of inborn deficiencies of arylsulfatases A and B.