Biosynthesis in vitro of a blood group B-active fucose-containing hexaglycosylceramide from neolactopentaosylceramide in bovine spleen.

A solubilized alpha-fucosyltransferase activity has been isolated from a bovine spleen Golgi-rich membrane fraction. The enzyme transfers fucose from GDP-beta-L-fucose to a blood group B-active pentaglycosylceramide acceptor (Gal(alpha 1-3)Gal(beta 1-4)GlcNAc(beta 1-3)Gal(beta 1-4)Glc-ceramide) isolated from rabbit erythrocytes. Treatment of the membranes with 0.2% (final concentration) sodium taurodeoxycholate detergent produced maximal recovery (90%) of activity. A cationic detergent, G-3634-A, is required for optimal activity and the enzyme does not require addition of exogenous metal ion for activation. The purified 14C-labeled product of the reaction migrated with human blood group B-active hexaglycosylceramide on Silica Gel G thin layer plates. After treatment with fig alpha-galactosidase, the radioactive pentaglycosylceramide migrated with human H-active glycosphingolipid. The 14C-labeled product inhibited the hemagglutination reaction of B-type erythrocytes with Bandeiraea simplicifolia lectin and anti-B serum and formed a precipitin line with Euonymus europeus lectin. Treatment of the 14C-labeled product with alpha-fucosidase (Venus mercenaria) or weak acid at 100 degrees C for 2 h released 80-90% of the bound radioactive fucose.