Enzymatic basis of sugar structures of α-fetoprotein in hepatoma and hepatoblastoma cell lines: Correlation with activities of α1–6 fucosyltransferase and N-acetylglucosaminyltransferases III and V



α-Fetoproteins (AFPs) were purified from 2 hepatoma cell lines (Hep G2 and HuH-7) and a hepatoblastoma cell line (HuH-6), and the structures of pyridylaminated (PA) derivatives of their sugar chains were analyzed by HPLC. Simultaneously, the activities of αl-6 fucosyltransferase (αl-6FT) and N-acetylglucosaminyltransferase III (GnT-III), IV(GnT-IV) and V(GnT-V) were assayed in these cell lines. For all 3 cell lines the major sugar chain detected was a fucosylated biantennary structure. Hep G2 cells contained a high level of GnT-V, which catalyzes the formation of a tri'-antennary structure, and in fact a substantial percentage of the AFP sugar chains in these cells had the tri'-antennary structure. αl-6FT was also high, and fucosylated tri' structures were detected, which suggests that high activities of transferases affect the AFP sugar chains. In HuH-6 cells, GnT-III, which catalyzes the formation of bisecting GIcNAc, was elevated. Correspondingly, a fucosylated, bisected biantennary structure was found as a major sugar chain. In the HuH-7 cell line, the contents of bisecting GIcNAc and tri' structure were low and neither GnT-III nor GnT-V was elevated. These data indicate that the sugar structures of AFP in these cell lines correlate well with the activities of αl-6 FT, GnT-III and GnT-V.