Purification and Characterization of a Lymph Node Sulfotransferase Responsible for 6-O-Sulfation of the Galactose Residues in 2′-Fucosyllactose and Other Sialyl LewisX-Related Sugars

A microsomal galactose-6-O-sulfotransferase (Gal-6-O-Stase) from porcine lymph nodes, able to transfer the sulfate group from adenosine 3′-phosphate 5′-phosphosulphate (PAPS) onto 2′-fucosyllactose (2′-FL) and other sialyl LewisX(sLex)-related sugars, has been purified and characterized. The enzyme was purified to about 35,000-fold by a combination of conventional and affinity chromatographic steps. The purified enzyme preparation exhibited two protein bands at around 80-90 and 170 kDa on 7.5% SDS-PAGE under reducing conditions. Both of these protein bands always comigrated in the gel when peak fractions containing Gal-6-O-Stase activity from the 3′,5′-ADP-agarose column were subjected to 6% SDS-PAGE under reducing conditions. These protein bands also showed similar binding patterns to WGA (wheat germ agglutinin), Con A (concanvalin A), and EBA (elderberry agglutinin). Similarly, when the enzyme preparation after the hydroxylapatite step was photolabeled with 8-azido-[32P]-PAPS, both 80-90 and 170 kDa protein bands were labeled in a specific manner. These results suggest a possible association of these two protein bands with the enzyme activity. The carbohydrate substrate specificity of this enzyme suggests that it is well suited to catalyze the sulphonation at the C-6 position of the galactose residues of oligosaccharides that are structurally similar to sLex. Furthermore, a survey of several porcine organs revealed that this enzyme was selectively expressed in lymphoid tissues such as lymph nodes (peripheral and mesenteric) and spleen. These findings suggest that this enzyme may be involved in the assembly of 3′-sialyl-6′-sulfo Lewisx, the major capping group of HEV-ligands for L-selectin.