CHARACTERIZATION AND BIOLOGICAL SIGNIFICANCE OF SIALYL SYL-BETA-1-4XYLOSYL-BETA-1-(4-METHYLUMBELLIFERONE) SYNTHESIZED IN CULTURED HUMAN SKIN FIBROBLASTS

Human skin fibroblasts were incubated in the presence of a fluorogenic xyloside, 4-methyl-umbelliferyl-beta-D-xyloside (Xyl-MU), then the cu ltured medium was recovered, concentrated with a lyophilizer, and dial yzed against distilled water. The structures of the Xyl-MU derivatives purified from the dialyzable fraction were investigated. In addition to established glycosaminoglycans-MU (GAGs-MU), Gal-Gal-Xyl-MU, Gal-Xy l-MU, sulphate-GlcA-Xyl-MU, GlcA-Xyl-MU, and Xyl-Xyl-MU, which were in duced by Xyl-MU, an oligosaccharide having fluorescence was purified u sing a combination of gel filtration, ion-exchange chromatography and high-performance liquid chromatography, then subjected to carbohydrate composition analysis, enzyme digestion, Smith degradation, H-1-NMR, a nd ion-spray mass spectrometric analysis. From the data obtained, the oligosaccharide was considered to have the structure SA alpha 2-3Gal b eta 1-4Xyl beta 1-MU. The amount of MU-oligosaccharide in the cell cul ture increased with time and was dependent on the amount of Xyl-MU add ed. Its production was also different from that of Gal-Gal-Xyl-MU and Gal-Xyl-MU, which are biosynthetic intermediates of GAG-MU. Addition o f CDP, an inhibitor of sialyltransferase, to the cell culture medium i ncreased the secretion of GAG-MU. These results suggest that SA-Gal-Xy l-MU production may be related to the regulation of GAG-MU biosynthesi s.