OLIGOSACCHARIDE REPROCESSING OF PLASMA MEMBRANE GLYCOPROTEINS

Abstract

Plasma membrane glycoproteins of rat liver and cultured rat hepatocytes may undergo continuous reprocessing of their oligosaccharide units by de- and reglycosylation of terminal Sugars. In distinct glycoproteins deglycosylation may also include core Sugars of the oligosaccharides. As shown for L-fucose, terminal sugars are presumably removed from the glycoproteins in a prelysosomal compartment. Both the extent and the rate of terminal deglycosylation are influenced by cell proliferation and transformation. Subsequent upon terminal deglycosylation plasma membrane glycoproteins may be refucosylated and resialylated as has been shown for dipeptidyl peptidase Iv (DPP IV). Oligosaccharide reprocessing most likely occurs during recycling of the glycoproteins in between the cell surface and intracellular compartments.