Arylsulfatase AArylsulfatase A is an enzyme that breaks down sulfatides, namely cerebroside 3-sulfate into cerebroside and sulfate. In humans, arylsulfatase A is encoded by the ARSA gene.Clinical significanceA deficiency in Arylsulfatase A is associated with metachromatic leukodystrophy, an autosomal recessive disease. Multiple sulfatase deficiency (MSD) is also associated with the ARSA gene.BiochemistryEnzyme regulationArylsulfatase A is inhibited by phosphate, which forms a covalent bond with the active site 3-oxoalanine.