N-Acetylgalactosamine-6-Sulfate Sulfatase in Human Placenta: Purification and Characteristics

Abstract

N-Acetylgalactosamine-6-sulfate sulfatase from human placenta was purified 33, 600-fold using β-N-acetyl-D-galactosamine 6-sulfate-(1→4)- β-D-glucuronic acid-(1→3) -N-acetyl-D- [³H]galactosaminitol 6-sulfate as the substrate. This enzyme is an oligomer with a molecular mass of 120 kDa and consists of polypeptides of 40 and 15 kDa. The 15 kDa polypeptide is a glycoprotein. This purified protein has activities of N-acetylgalacto-samine-6-sulfate sulfatase and galactose-6-sulfate sulfatase. Rabbit antiserum was raised against the purified protein. The antibody titrated N-acetylgalactosamine-6-sulfate sul-fatase and galactose-6-sulfate sulfatase. The size of the precursor of the enzyme is 60 kDa, as determined by cell-free translation. The optimal pH values of the N-acetylgalacto-samine-6-sulfate sulfatase and galactose-6-sulfate sulfatase activities are pH 3.8-4.0, and the K_ms are 8 and 13 μM, respectively. Sulfate and phosphate ions are potent competitive inhibitors for the enzyme and their inhibition constants are 35 and 200μM, respectively. Cross-reactive materials of 40 and 15 kDa were detected by immunoblot analysis, in the placenta, liver, and normal fibroblasts, but not in fibroblasts from a patient with Morquio disease.