Enzymatic sulfation of mucus glycoprotein in rat submandibular salivary gland

1. 1. The enzymic activity which catalyzes transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to mucus glycoprotein was found associated with Golgi-rich membrane fraction of rat submandibular salivary gland. 2. 2. Optimum enzyme activity was obtained with 0.5% Triton X-100, 4mM MgCl₂ and 25 mM NaF at a pH of 6.8 using desulfated submandibular salivary mucus glycoprotein. The apparent K_m of the enzyme for mucus glycoprotein was 11.1 mg/ml. 3. 3. Alkaline borohydride reductive cleavage of the synthesized ³⁵S-labeled glycoprotein led to the liberation of the label into reduced oligosaccharides. A 75.4% of the label was found incorporated in four oligosaccharides. These were identified in order of abundance as sulfated penta-, tri-, hepta- and nonsaccharides. 4. 4. Based on the results of chemical and enzymatic analyses of the intact and desulfated compounds the pentasaccharide was characterized as SO₃ H → GlcNAcβ → Galβ → GlcNAc(NeuAcα →) GalNAc-ol and the trisaccharide as SO₃ H →GlcNAcβ →Galβ → GalNAc-ol.