Glycosyltransferase and Sulfotransferase Activities in Chick Corneal Stromal Cells before and afterin VitroCulture

The expression type of proteoglycan in corneal stromal cells is known to change markedly when the cells are culturedin vitro.To determine which enzyme is primarily responsible for this change in chick corneal stromal cells, the activities of various glycosyltransferases and sulfotransferases were determined before and afterin vitroculture of the cells. The activities ofN-acetylglucosaminyltransferase, galactosyltransferase, and sulfotransferase, which are involved in keratan sulfate synthesis, were assayed using pyridylaminatedN-acetyllactosamine-containing oligosaccharides as acceptor substrate; the activities ofN-acetylgalactosaminyltransferase, glucuronyltransferase, and sulfotransferase, which are involved in chondroitin sulfate synthesis, were assayed using pyridylaminated chondrooligosaccharides as acceptor substrate. Of these enzymes, the sulfotransferase activity toward degalactosylated, pyridylaminated lacto-N-neotetraose andN-acetyllactosamine dimer (probably GlcNAc-6-sulfotransferase) decreased markedly afterin vitroculture, whereas the galactosyltransferase activity increased. The chondroitin sulfate–sulfotransferase activities toward pyridylaminated chondrooligosaccharides hardly changed afterin vitroculture. The marked decrease in the activity of the keratan sulfate-sulfotransferase corresponds to the marked decrease in keratan sulfate biosynthesis when the cells are culturedin vitro.These findings suggest that keratan sulfate-sulfotransferase (GlcNAc-6-sulfotransferase) is a key enzyme in keratan sulfate biosynthesis and that its decrease is primarily responsible for the marked decrease in keratan sulfate synthesis afterin vitroculture.