An adult-type metachromatic leukodystrophy caused by substitution of serine for glycine-122 in arylsulfatase A.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease with autosomal recessive inheritance caused by a deficiency of the enzyme arylsulfatase A (ASA). We have identified a new mutation in the ASA gene of a patient with adult-type MLD. In this mutation, the glycine at position 122, a highly conserved residue in the AS gene family, was replaced by serine. In a transient expression study, COS cells transfected with the mutant cDNA carrying 122Gly-->Ser did not show an increase of ASA activity and produced little material immunoreactive to an anti-ASA antibody, despite normal mRNA levels.