Faculty Bibliography

A simple assay technique for the determination of sulfatidase activity in leukocytes has been developed for the reliable diagnosis of metachromatic leukodystrophy (MLD). Sulfatide is tritiated in sphingosine and fatty acid by reduction with [3H]sodium borohydride in alkali in the presence of palladium chloride. This labeled natural substrate for aryl sulfatase A (AsA) is hydrolyzed by normal human leukocytes in 25 mM-acetate buffer, pH 5.0, in the presence of 0.3% sodium taurodeoxycholate. The enzyme activity is greatly improved after dialysis, exhibiting better linearity with protein concentration. It is stimulated maximally by 5 mM-MnCl2 with an apparent Km of 0.17 mM for the substrate. Patients with MLD exhibited virtually no detectable sulfatidase activity although they had residual AsA activity that was measured with the synthetic substrate, p-nitrocatechol sulfate (NCS). Potential heterozygotes could be identified by the sulfatidase assay in instances where the NCS assay for AsA was inconclusive. Several individuals with levels of AsA activity characteristic of MLD, including a few healthy carriers and certain patients with unknown neurological diseases, were shown not to have MLD by the presence of measurable levels of sulfatidase in their leukocytes

A family exhibiting a leukocytic arylsulfatase A deficiency, probably inherited in an autosomal recessive manner, differed from patients with typical metachromatic leukodystrophy in that sulfatiduria was absent and there was readily detectable cerebroside sulfatase activity. To our knowledge, this family was unique in that there were no known members with metachromatic leukodystrophy and the only neurologic abnormality was progressive retinal pigment degeneration in the proband