Glycobiology, 2001, Vol. 11, No. 5 353-363
© 2001 Oxford University Press
Human lung adenocarcinoma 
1,3/4-L-fucosyltransferase displays two molecular forms, high substrate affinity for clustered sialyl LacNAc type 1 units as well as mucin core 2 sialyl LacNAc type 2 unit and novel 1,2-L-fucosylating activity
Molecular and Cellular Biophysics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
Human lung tumor 
1,3/4-L-fucosyltransferase (FT) was purified (2000-fold, 29% recovery) from 290 g of tissue by including a chromatography step on Affinity Gel-GDP. Two molecular forms (FTA, larger size carrying 15% 1,4-FT activity; FTB, the major form with 85% activity) were separated by further fractionation on a Sephacryl S-100 HR column. A difference in the electrophoretic mobilities of these two activities was also found on native polyacrylamide gel electrophoresis (PAGE). Both forms were devoid of typical 1,2-fucosylating activity but were associated with the novel 1,2-fucosylating ability of converting the Lewis a determinant to Lewis b. Based on percentage activity toward 2-O-MeGalß1,3GlcNAcß-O-Bn, both forms exhibited the same extent of activity toward various acceptors, which included sulfated, sialylated, or methylated LacNAc type 1 or type 2 as well as mucin core 2 acceptors. However, FTA and FTB exhibited a difference in their ability to act on mucin core 2 3'-sialyl LacNAc (activities 24.2% and 40.8%, respectively, as compared to 2-O-MeGalß1,3GlcNAcß-O-Bn). The unsubstituted LacNAc type 1 acceptors were 15–20 times as active as the corresponding LacNAc type 2 acceptors. The 3-O-substitution on the ß1,4-linked Gal (methyl, sulfate, or sialyl) in mucin core 2 acceptors increased the efficiency of these acceptors five- to eightfold. The most efficient acceptor for FTA and FTB was 3-O-sulfoGalß1,3GlcNAcß-O-Al (Km 100 and 47 µM, respectively). The Km (mM) values for 2-O-methyl Galß1,3GlcNAcß-O-Bn and 3-O-sialyl Galß1,3GlcNAcß-O-Bn were 0.40 and 2.5 (FTA) and 0.16 and 0.67 (FTB), respectively.
The 35-kDa glycoprotein ancrod (from Malayan pit viper venom) containing 36% complex N-glycans with the antennae NeuAc2,3Galß1,3GlcNAcß- acted as the best macromolecular acceptor substrate (Km: 45 µM), as examined with FTB. On desialylation the acceptor efficiency dropped to 
50% (Km for asialo ancrod: 167 µM). Sialylglycoproteins, such as carcinoembryonic antigen, fetuin, and bovine 1-acid glycoprotein, were better acceptors than asialo fetuin. On the contrary, fetuin triantennary glycopeptide containing predominantly NeuAc2,3Galß1,4GlcNAcß- was only 55% active as compared to the asialo glycopeptide (Km: 1.43 and 0.63 mM, respectively). Thus, the human lung tumor 1,3/4-L-FT has the potential to generate clustered sialyl Lewis a and Lewis b determinants in N-glycans and sialyl Lewis x determinant in mucin core 2 structures.
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