The ARSA gene is located on chromosome 22q13.33 and gives instruction for making a lysosomal enzyme of 507 amino acids called arylsulfatase A. This enzyme hydrolyzes cerebroside sulfate to cerebroside and sulfate. Defects in the arylsulfatase A enzyme are the cause of metachromatic leukodystrophy (MLD), a lysosomal storage disease.