Human liver N-acetylgalactosamine 6-sulphatase. Purification and characterization

J. Bielicki, J. J. Hopwood

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Abstract

Human N-acetylgalactosamine 6-sulphatase (EC 3.1.6.14), which is involved in the lysosomal degradation of the glycosaminoglycans keratan sulphate and chondroitin 6-sulphate, was purified more than 130,000-fold in 2.8% yield from liver by an eight-step column procedure. One major form was identified with a pl of 5.7 and a native molecular mass of 62 kDa by gel filtration. When analysed by SDS/PAGE, dithioerythritol-reduced enzyme contained polypeptides of molecular masses 57 kDa, 39 kDa and 19 kDa, whereas non-reduced enzyme contained a major polypeptide of molecular mass 70 kDa. It is proposed that active enzyme contains either the 57 kDa polypeptide or disulphide-linked 39 kDa and 19 kDa polypeptides. Minor amounts of other enzyme forms separated during the chromatofocusing step and the Blue A-agarose step were not further characterized. Purified N-acetylgalactosamine 6-sulphatase was inactive towards 4-methylumbelliferyl sulphate, but was active, with pH optima of 3.5-4.0, towards 6-sulphated oligosaccharide substrates. K(m) values of 12.5 and 50 μM and V(max) values of 1.5 and 0.09 μmol/min per mg were determined with oligosaccharide substrates derived from chondroitin 6-sulphate and keratan sulphate respectively. Sulphate, phosphate and chloride ions were inhibitors of enzyme activity towards both substrates, with 50 μM-Na2SO4 giving 50% inhibition towards the chondroitin 6-sulphate trisaccharide substrate.

Original languageEnglish
Pages (from-to)515-520
Number of pages6
JournalBiochemical Journal
Volume279
Issue number2
DOIs
Publication statusPublished - 1 Jan 1991

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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