The Sanfilippo A corrective factor. Purification and mode of action.

Fibroblasts from patients with the Sanfilippo syndrome fall into two subgroups, each manifesting a deficiency of a specific factor required for normal metabolism of sulfated mucopolysaccharide. The factor deficient in the A subgroup has been purified 850-fold from normal human urine by ammonium sulfate precipitation, successive chromatography on Sephadex G-ZOO, carboxymethylcellulose, and hydroxylapatite, and finally, by polyacrylamide gel electrophoresis. The best preparation, estimated to be about 40% pure, was free of factors specific for other mucopolysaccharidoses, as well as of several lysosomal enzymes found in urine: P-n-galactosidase, N-acetyl-a-n-glucosaminidase and N-acetyl-a-o-galactosaminidase, ,L?-D-glucuronidase, and arylsulfatase B. It was, however, somewhat contaminated with aryl sulfatase A, and markedly so with N-acetyl-P-n-glucosaminidase and N-acetyl-fi-D-galactosaminidase. The factor accelerates degradation of stored mucopolysaccharide in Sanfilippo A fibroblasts, as indicated by chase experiments. After the factor is removed from the medium, its effect persists in the cells with a half-life of 2 days. Incubation of stored mucopolysaccharide (tentatively identified as heparan sulfate with a high N-sulfate content) with purified factor resulted in release of inorganic sulfate. It is suggested that the Sanfilippo A factor is a heparan sulfate sulfatase.