Growth-associated glycosylation of transferrin secreted by HepG2 cells.

Growth-associated alterations in the oligosaccharide structures of transferrin secreted by HepG2 cells were examined by concanavalin A-crossed affinoimmuno-electrophoresis. Slowly dividing, confluent cultures produced transferrin with a approximately 4.5-fold greater proportion of biantennary complex-type oligosaccharides than rapidly dividing, subconfluent cultures. The activity of N-acetylglucosaminyltransferase V (GlcNAc-T V) and galactosyltransferase were measured in cell extracts from subconfluent and confluent cultures. While the activity of galactosyltransferase remained relatively constant, the activity of GlcNAc-T V was approximately 3.2-fold lower in confluent cultures than in subconfluent cultures. These results suggest that the growth-associated alteration in the oligosaccharides of transferrin is due, at least in part, to the regulation of GlcNAc-T V activity.