GLYCOSYLATION OF GAMMA-GLUTAMYL-TRANSFERASE IS MODIFIED BY ETHANOL INH5-6 HEPATOMA-CELL LINE

The H5-6 cultured rat hepatoma cell line was used to investigate the p ost-translational maturation of gamma-glutamyltransferase (GGT) and th e effects of acute ethanol administration on the expression and glycos ylation of this membrane-bound glycoprotein. We found that the two sub units of H5-6 GGT with molecular masses of 55 and 33 kDa were derived from a single glycosylated precursor of 80 kDa. In addition, signals o f high molecular mass (more than 90 kDa) were detected. In vitro degly cosylation experiments indicated that N-linked sugars represented abou t 25% of the molecular weight of the H5-6 enzyme. By use of serial lec tin affinity technique, we showed that N-linked sugar chains were main ly of the biantennary complex and hybrid-type, without fucose linkage to the innermost N-acetyl-glucosamine. Ethanol treatment did not seem to affect the expression of GGT and the sialic acid content of the enz yme, but altered its oligosaccharide chain composition both quantitati vely and qualitatively.