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Leukocyte Sulfatidase for the Reliable Diagnosis of Metachromatic Leukodystrophy
Author(s) -
Raghavan S. S.,
Gajewski A.,
Kolodny E. H.
Publication year - 1981
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1981.tb01648.x
Subject(s) - metachromatic leukodystrophy , arylsulfatase a , chemistry , substrate (aquarium) , sodium , sulfatase , dialysis , biochemistry , chromatography , enzyme , medicine , endocrinology , biology , ecology , organic chemistry
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 [ 3 H]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 mwacetate 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‐MnCl 2 with an apparent K m 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.