A Cloned Human DNA Restriction Fragment Determines Expression of a GDP-L-fucose:β-D-Galactoside 2-α-L-fucosytransferase in Transfected Cells

Variations in human liver fucosyltransferase activities in hepatobiliary diseases

The hyperfucosylation of a number of glycoconjugates observed in liver diseases involves the action of several specific fucosyltransferases (F.T.) notably responsible for synthesizing histo-blood group antigens. We determined the activities of alpha 3, alpha 2 and alpha 3/4 F.T. in 35 liver biopsy samples from patients with fatty liver, alcoholic or post-hepatic liver cirrhosis, primary or secondary biliary cirrhosis, acute hepatitis or a normal liver. F.T. activities were measured by transfer of GDP [14C] fucose to asialotransferrin for alpha 3 F.T., to phenyl beta-D-galactoside for alpha 2 F.T. and to 2' fucosyllactose for alpha 3/4 F.T. The diseased liver extracts showed an early increase in non-Le gene-associated alpha 3 F.T. activity (p = 0.001), which was related to the number of steatosic hepatocytes and the degree of intralobular inflammatory infiltration. Overexpression of this alpha 3 F.T. provides an explanation for the strong expression of 3-fucosyl lactosamine structures described in several hepatobiliary diseases. alpha 2 F.T. levels were significantly elevated in the two groups of liver cirrhosis and acute hepatitis (p = 0.05), but not enough to consider alpha 2 F.T. as a sensitive feature of mesenchymal cell injury. All Lewis-positive biopsies displaying biliary alterations showed increased Le gene-encoded alpha 3/4 F.T. activity (p = 0.001), which was related to the intensity of neoductular proliferation. Elevated levels of alpha 3/4 F.T. may be a very early sign of biliary regeneration.

Enzyme-catalyzed oligosaccharide synthesis

Cell-surface carbohydrates and their conjugates are involved in many types of molecular recognition. This review describes recent developments in enzyme-catalyzed oligosaccharide synthesis, with particular focus on glycosyltransferase and glycosidase reactions. With the increasing availability of glycosyltransferases via recombinant DNA technology, glycosyltransferase-catalyzed glycosylation with in situ regeneration of sugar nucleotides appears to be the most effective method for large-scale stereocontrolled oligosaccharide synthesis.

ELFT: a gene that directs the expression of an ELAM-1 ligand

The LECCAMs are a family of cell adhesion molecules implicated in certain inflammatory processes. ELAM-1, a LECCAM found on the surface of activated endothelial cells, can mediate adhesion of neutrophils, monocytes, and certain cell lines to endothelial cells in vitro. No ligand for any LECCAM has yet been fully characterized. Here we report the cloning of a cDNA, ELFT (ELAM-1 ligand fucosyltransferase), that can confer ELAM-1 binding activity when transfected into nonbinding cell lines. ELFT encodes a 46 kd protein that has alpha(1,3)fucosyltransferase activity, suggesting that a fucosylated carbohydrate structure is an essential component of the ELAM-1 ligand. Furthermore, ELFT is expressed specifically in cell types that bind to ELAM-1, suggesting that this enzyme is an important regulator of inflammatory events in vivo.

ELAM-1--dependent cell adhesion to vascular endothelium determined by a transfected human fucosyltransferase cDNA

Adhesion of circulating leukocytes to the vascular endothelium during inflammation is mediated in part by their interaction with the endothelial-leukocyte adhesion molecule ELAM-1. ELAM-1, a member of the LEC-CAM family of cell adhesion molecules, expresses an N-terminal carbohydrate recognition domain (CRD) homologous to various calcium-dependent mammalian lectins. However, the contribution of the CRD to cell adhesion and its carbohydrate binding specificity have not been elucidated. This study demonstrates that transfection of a human fucosyltransferase cDNA into nonmyeloid cell lines confers ELAM-1--dependent endothelial adhesion. Binding activity correlates with de novo cell surface expression of the sialylated Lewis x tetrasaccharide, whose biosynthesis is determined by the transfected fucosyltransferase cDNA. We propose that specific alpha(1,3)fucosyltransferases regulate cell adhesion to ELAM-1 by modulating cell surface expression of one or more alpha(2,3)sialylated, alpha(1,3)fucosylated lactosaminoglycans represented by the sialyl Lewis x carbohydrate determinant.

A cloned human cDNA determines expression of a mouse stage-specific embryonic antigen and the Lewis blood group alpha(1,3/1,4)fucosyltransferase

The stage-specific embryonic antigen SSEA-1 is a cell-surface oligosaccharide molecule expressed with temporal precision during the murine preimplantation period and implicated in adhesive events involving the process of compaction. We used a mammalian transient expression system to isolate a cloned human cDNA that determines expression of the SSEA-1 molecule. The cDNA sequence predicts a type II transmembrane protein with a domain structure similar to mammalian glycosyltransferases, but without primary sequence similarity to these enzymes. The carboxy-terminal domain of this protein was shown to be catalytically active as a fucosyltransferase when expressed in COS-1 cells as a portion of a secreted protein A fusion peptide. The enzyme is an exceptional glycosyltransferase in that it can use both type I and type II oligosaccharides as acceptor substrates to generate subterminal Fuc alpha(1,4)- and Fuc alpha(1,3)-linkages, respectively, in a manner analogous to the human Lewis blood group fucosyltransferase. Southern blot analysis shows that the cDNA corresponds to sequences syntenic to the Lewis locus on chromosome 19. These results indicate that this cDNA is the product of the human Lewis blood group locus, provide genetic confirmation of the hypothesis that this enzyme can catalyze two distinct transglycosylation reactions, and outline an approach to the isolation of other sequences that determine expression of developmentally regulated oligosaccharide antigens.

Genetic control of the fucosylation of ABH precursor chains. Evidence for new epistatic interactions in different cells and tissues

The general structure of the ABH antigens is analysed taking into account six possible precursor chains and two alpha-2-fucosyltransferases. The classical genetic model with one structural gene and two regulatory genes for the synthesis of the H antigen and the events which prompted the proposal of the new model with two structural genes for the synthesis of H determinants are discussed. Three human alpha-3-fucosyltransferases with different acceptor specificity are presented. Myeloid type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2, serum type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2 and sialyl-N-acetyl-lactosamine and Lewis or alpha-3/4-fucosyltransferase, which transfers fucose on to H type 1 and H type 2 and the corresponding sialylated structures. The presence of different ABH and Lewis antigens in different tissues and the different epistatic interactions needed to account for their synthesis are analysed in terms of new epistatic interactions with either the known fucosyltransferases or with new fucosyltransferases.

Purification of the blood group H gene associated alpha-2-L-fucosyltransferase from human plasma

The alpha-2-L-fucosyltransferase in human plasma has been freed from alpha-3-L-fucosyltransferase activity and purified approximately 200,000-fold by a series of steps involving ammonium sulphate precipitation, hydrophobic chromatography on Phenyl Sepharose 4B and affinity chromatography first on GDP-adipate-Sepharose and then on GDP-hexanolamine-Sepharose. The purified alpha-2-L-fucosyltransferase had a M(r) on gel filtration HPLC of 158,000 and showed optimal activity in the pH range 6.5-7.0. The enzyme transferred fucose equally well to Type 1 (Gal beta 1-3GlcNAc) and Type 2 (Gal beta 1-4GlcNAc) substrates but Type 3 (Gal beta 1-3GalNAc) structures were less efficient acceptors. Competition experiments indicated that a single enzyme species in the purified preparation was responsible for reactivity with the Type 1 and Type 2 structures. Thus the differences in conformation between the Type 1 and Type 2 disaccharides do not appear to influence the capacities of their terminal non-reducing beta-D-galactosyl residues to function as acceptor substrates for the alpha-2-L-fucosyltransferase expressed by the blood group H gene in haemopoietic tissue.