The structures of sugar chains of γ-glutamyl transpeptidases (γ-GTP) purified from rat liver and rat ascites AH-66 hepatoma were comparatively studied. The number of sugar chains in one molecule of hepatoma γ-GTP was approximately four times higher than that of liver γ-GTP. Only acidic sugar chains were found in liver γ-GTP, while hepatoma enzyme contained approximately 30% of neutral sugar chains which were high mannose type and complex type. The acidic sugar chains of liver γ-GTP were sialylated bi-, tri-, tetraantennary sugar chains and tetraantennary sugar chains with Galβ1→GlcNAc repeating outer chains. In contrast, no Galβ1→GlcNAc repeating outer chain was found in the acidic sugar chains of hepatoma enzyme. No bisect N-acetylglucosamine residue was found in the sugar chains of liver enzyme like liver enzymes of other animals, while some of hepatoma enzyme did contain this residue. Furthermore, some of the outer chain moieties of the complex type sugar chains of hepatoma γ-GTP did not contain galactose residue indicating that the deletion phenomena as found in the glycolipids of cancerous tissues were included in the biosynthesis of these sugar chains. These results indicate that the glycosylation of hepatoma γ-GTP is not strictly controlled as in the case of liver γ-GTP.
抄録全体を表示