Specificity of fucose transfer to GlcNAc residues of extended chain neolacto-series glycolipids catalyzed by human alpha 1-->3fucosyltransferases: effect of the lipidic environment on the myeloid enzyme form

Abstract

Multiple alpha 1-->3fucosyltransferases occur in the human genome of which the Lewis (FucT-III), myeloid (FucT-IV), and plasma (FucT-V) enzyme forms have received the greatest attention. In this paper, the acceptor properties of the myeloid alpha 1-->3fucosyltransferase from human promyelocytic leukemia HL-60 cells have been studied. Fucose transfer into glycolipid acceptors was activated by detergents G-3634-A or taurodeoxycholate resulting in efficient transfer to neutral acceptors but poor transfer to sialylated acceptors, characteristic of the myeloid-type enzyme. Fucose transfer to nLc6 yielded both mono- and difucosyl derivatives under both detergent conditions. The nLc6 monofucosyl products were isolated and analyzed by TLC immunostaining and fast atom bombardment-mass spectroscopy analysis. The G-3634-A monofucosyl product was found to be composed solely of V3FucnLc6, whereas that with taurodeoxycholate was determined to be a mixture of III3FucnLc6 and V3FucnLc6 in near equal amounts. Analysis of reaction products using enzyme activation by phospholipids indicated that phosphatidylethanolamine and phosphatidylinositol behaved similarly to G-3634-A. In contrast, phosphatidylglycerol yielded results similar those of taurodeoxycholate. Fucose transfer to VI3NeuAcnLc6 yielded approximately 75% of the product as the III-GlcNAc monofucosyl derivative regardless of the detergent or phospholipid condition used. Analysis of fucose transfer to nLc6 catalyzed by the Lewis enzyme from Colo 205 cells using taurodeoxycholate yielded solely the III-GlcNAc monofucosyl derivative, whereas the predominant product with G-3634-A was V-GlcNAc fucosylated. In contrast, under both conditions only the V-GlcNAc monofucosylation product was found with the enzyme from NCI-H69 cells. The results indicate that subtle intrinsic differences exist between human alpha 1-->3fucosyltransferases. Modulation of enzyme specificity via the nature of the membrane environment could participate in regulation of expression of distinct cell surface antigens.