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The partial characterization of the epithelial glycoprotein from normal and diseased colons Tsang, Wai-Chiu


This study reports the isolation, fractionation and chemical characterization of apparently homogenous and undegraded epithelial glycoproteins from normal human colons and from patients with ulcerative colitis, Crohn's disease and ischaemic colitis of the colon. Colonic epithelial cells were removed from each specimen by shaking with EDTA and the glycoproteins were extracted'from the sonated cells with 1M NaCl. Combined agarose gel and DEAE cellulose chromatography of the pooled crude extract from each normal and diseased sample yielded two apparently homogeneous fractions A and B. Agarose gel electrophoresis revealed that the mobility of the second DEAE fraction (B) was about the same as that of heparin and twice as fast as that of fraction A. Application of gas-liquid chromatography, UV-spectroscopy, agarose gel electrophoresis at pH 3.0, colorimetric hexose analysis, phosphorus and Indole assays suggested that fraction B was DNA. Fraction A glycoproteins appeared to be homogeneous by DEAE chromatography, agarose gel and cellulose acetate electrophoreses at pH 8.8. Chemical analyses of these glycoproteins revealed the presence of fucose, galactose, hexosamine, sialic acid, protein and little or no phosphorus. The molar ratio of the carbohydrate components of each sample was significantly different from that of the normal, and it varied among the different diseases. In each of the glycoproteins studied, 4 different types of sialic acids were found in different quantities and they were: (1)unsubstituted or C9 substituted sialic acids, (ii) sialic acids substituted at C4 and or at C9, (iii) sialic acids substituted at C7 and or C8, (iv) sialic acids substituted at C4 and at C7 and or C8. Gas-liquid chromatography revealed that these substituents were alkaline-labile O-acetyl groups. The significance of the above differences were discussed.

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