Human colon
carcinoma cell
fucosyltransferase (FT) in contrast to the FTs of several human
cancer cell lines, utilized GlcNAcbeta1,4GlcNAcbeta-O-Bn as an acceptor, the product being resistant to alpha1,6-L-Fucosidase and its formation being completely inhibited by LacNAc Type 2 acceptors. Further, this
enzyme was twofold active towards the asialo agalacto
glycopeptide as compared to the parent asialoglycopeptide. Only 60% of the GlcNAc moieties were released from [14C]fucosylated asialo agalacto triantennary
glycopeptide by jack bean
beta-N-acetylhexosaminidase. These alpha1,3-L-fucosylating activities on multiterminal GlcNAc residues and
chitobiose were further examined by characterizing the products arising from
fetuin triantennary and bovine
IgG diantennary
glycopeptides and their
exoglycosidase-modified derivatives using
lectin affinity chromatography. Utilization of [14C]fucosylated
glycopeptides with cloned FTs indicated that
Lens culinaris lectin and
Aleuria aurantia lectin (AAL) required, respectively, the diantennary backbone and the
chitobiose core alpha1,6-fucosyl residue for binding. The outer core alpha1,3- but not the alpha-1,2-fucosyl residues decreased the binding affinity of AAL. The AAL-binding fraction from [14C]fucosylated
asialo fetuin, using colon
carcinoma cell extract, contained 60% Endo F/PNGaseF resistant chains. Similarly AAL-binding species from [14C]fucosylated TFA-treated bovine
IgG using colon
carcinoma cell extract showed significant resistance to endo F/PNGaseF. However, no such resistance was found with the corresponding AAL non- and weak-binding species. Thus colon
carcinoma cells have the capacity to fucosylate the
chitobiose core in
glycoproteins, and this alpha1,3-L-fucosylation is apparently responsible for the AAL binding of
glycoproteins. A cloned FT VI was found to be very similar to this
enzyme in acceptor substrate specificities. The
colon cancer cell FT thus exhibits four catalytic roles, i.e., alpha1,3-L-fucosylation of: (a) Galbeta1,4GlcNAcbeta-; (b) multiterminal GlcNAc units in complex type chain; (c) the inner core
chitobiose of
glycopeptides and
glycoproteins; and (d) the nonreducing terminal chiotobiose unit.