A simple chromogenic assay for arylsulfatase A.

Arylsulfatase A hydrolyzes the artificial chromogenic substrate 4-nitrocatechol-sulfate at 0 degree C at a rate of 24% of that at 37 degrees C whereas arylsulfatase B is almost inactive at 0 degree C. Based on this observation, a simple assay was developed which permits the accurate determination of low residual arylsulfatase A activities in cultured skin fibroblasts of infantile, juvenile and adult MLD patients and pseudodeficient individuals. In cultured skin fibroblasts, the following residual activities were found with this assay system: late-infantile patients, 0.0%, one juvenile patient, 1.0%, adult patients, 4.4-14% of normal average. healthy pseudodeficient probands ranged between 18% and 32%.