p.Nitrocatechol Sulfate for Arylsulfatase Assay: Detection of Metachromatic Leukodystrophy Variants

Artificial substrates are being used routinely for the diagnosis of lipidosis. In the case of metachromatic leukodystrophy (MLD), p.nitrocatechol-sulfate (p.NCS) at acidic pH is the substrate for arylsulfatase A (ASA). Complete analogy of elution profile on column chromatography between ASA and cerebroside sulfate sulfatase (1) has secured in the use of the artificial substrate for MLD diagnosis. Although an activator protein is necessary for enzyme action on the natural substrate (2), only the ASA enzyme itself is deficient in MLD variant B (3). Another enzyme arylsulfatase B (ASB) reacts with p.NCS at less acidic pH; together with ASA and other sulfatases, it is deficient in another type of sulfatidosis, Austin’s disease or MLD variant O (3).