A-L-Fucosyl

This class of enzymes includes galactoside 3(4)-L-fucosyl-transferase, [EC 2.4.1.65] glycoprotein 6-a-L-fucosyl-transferase [EC 2.4.1.68], galactoside 2-ce-L-fucosyltran-sferase [EC 2.4.1.69], and galactoside 3-fucosyltransferase [EC 2.4.1.152]. 

Galactoside 2-L-fucosyltransferase [EC 2.4.1.69], also known as blood group H a-2-fucosyltransferase, catalyzes the reaction of GDP-L-fucose with /8-D-galacto-syl-R to produce GDP and a-L-fucosyl-l,2-/3-D-galac-tosyl-R. Lactose can also act as the acceptor substrate. 

For the synthesis of the tetrasaccharide unit (267) of the blood-group substance A (type 1), Paulsen and Kolar [192, 193] prepared the benzoate (269) by partial benzoyl-ation of the diol (268) and condensed this with 2,3,4-tri-O-benzyl-a-L-fucosyl bromide in the presence of tetraethylammonium bromide to give (270) in 82% yield. The benzoyl group was removed to give (271) and this was condensed with the chloride (274) in the presence of silver carbonate — silver perchlorate to give the tetrasaccha-... 

Khorlin and co-workers [194, 195] prepared the blood-group A (type 1) tetrasaccharide (267) from the chloroacetate (272). This was condensed with 2-O-benzyl-3,4-di-O-p-nitrobenzoyl-a-L-fucopyranosyl bromide to give the 2-O-a-L-fucosyl derivative and after removal of the chloroacetyl group with thiourea the product was... 

Nashed and Anderson [155] prepared an isomer of the blood-group B (type 2) tetrasaccharide with lactosamine substituted at the 4 -position with an a-D-galactosyl residue and at the 2 -position with an a-L-fucosyl residue. For this purpose, the lactosamine derivative (331), prepared via (330), was a-glycosylated with tetrabenzyl-galactosyl bromide in the presence of silver carbonate and silver triflate and the benzoyl group removed from the product so that the 2 -position could be fucosylated with the bromide (302) in the presence of bromide ion. If the fucose residue was added first to the lactosamine derivative (332), then the product (333) [which was converted into the trisaccharide of the blood group H (type 2)] would not react with the tetrabenzyl-galactosyl bromide. 

Two pentasaccharides occur in the mixture of milk oligosaccharides. Lacto-iV-fucopentaose I readily gives an alkali-stable disaccharide, 2-0-(a-L-fucosyl)-D-galactose on alkaline degradation knowledge of the structure of this disaccharide, together with data from methylation studies, leads to the assignment of the structure of an a-L-fucosyl-(lacto-iV-tetraose) for the pentasaccharide.273... 

Lacto-N-fucopentaose II also contains an a-L-fucosyl residue linked to a lacto-iV-tetraose molecule, but in this case it is linked to C4 of the 2-acet-amido-2-deoxy-D-glucose unit. The sequence and linkages were again established by hydrolysis of the permethylated saccharide alcohol.279... 

On gel electrophoresis, the purified antibody preparations yield single bands when the gel is stained for proteins. However, on gel isoelectrofocus-ing, differences in the results maybe noted, as shown in Fig. 15. Several protein isomers were present in each antibody preparation, with 7 isomers being detected in the anti-BSA antibodies (B) and 11 isomers in the anti-fucose antibodies (F). The coupled electrofocusing-agar diffusion method showed that each isomer of the anti-fucose set possessed the same antibody activity with the antigen, a-L-fucosyl-BSA. 

Ajisaka K, Shirakabe M. Regioselective synthesis of a-L-fucosyl-containing disaccharides by use of a-L-fucosidases of various origins. Carbohydr. Res. 1992 224 291-299. 

Lacto-N-fucopmtaose II or monofuco-lacto-JV-tetraose II (4% of the total oligosaccharides) is also an a-L-fucosyl derivative of lacto-iV-tetraose, but, in this case, the substitution is on C-4 of the 2-acetamido-2-deoxy-D-glucose residue, that is, it is 0-j8-D-galactopyranosyl-(l 3)-0-[a-L-fucopyranosyl-(l —> 4)]-0-(2-acetamido-2-deoxy-i8-D-glucopyranosyl)-(l 3)-0-j8-D-galactopyranosyl-(l 4)-D-glucopyranose (22). 

Lacto- N-difucohexaose (7% of the total oligosaccharides) has not yet been fully characterized, but it appears to be a di-O-fucosyl derivative of lacto-Af -tetraose in which the a-L-fucosyl residues are linked to C-2 of the terminal n-galactose residue (as in lacto-AT-fucopentaose I) and to C-4 of the 2-acetamido-2-deoxy-D-glucose residue (as in lacto-iV-fucopentaose II). ... 

ReTioselective glycosylation of 38 with 2.3,4-tri-0-benzoyl-6-0-bcn2yl-a-D-galacto- 1 U -Z (VJ I and the followine 3-0-a-L-fucosylation of 39 gave the Lewis ... 

A fundamental finding revealed that the high affinity binding of N-linked glycopeptides to the pea (and lentil) lectins requires the presence of an a-L-fucosyl residue attached to the asparagine-linked A-acetylglucosamine residue [90,95]. 

The presence of an a-L-fucosyl group attached to the asparagine-linked iV-acetyl-glucosamine residue is an absolute requirement for the binding of glycopeptides and oligosaccharides of the poly-iV-acetyllactosamine type to the lentil lectin [90,95]. 

The most potent inhibitor described thus far is the type A disaccharide GalNAc(al-3)Gal. However, the addition of an a-L-fucosyl group to the Gal, as occurs in the type A trisaccharide, greatly diminished its activity [168]. A hydrophobic site on soybean agglutinin was identified by its interaction with A-dansylgalactosamine [169]. The soybean lectin possesses four carbohydrate binding sites per molecule, one for each subunit [169]. 

Carbohydrate-binding studies indicate strong preference for 2-0-linked a-L-fucosyl units, the best trisaccharide inhibitor of the lectin being L-Fuc(al-2)Gal( 3l-4)Glc. 

Although of animal origin, the lectin from the eel Anguilla anguilla) is an interesting and useful reagent with anti-O(H) activity [225]. It is specific for a-L-fucosyl groups. 

Oligosaccharides of mammalian milk contain a-L-fucosyl residues. In particular, the oligosaccharides in human milk play a protective role against infectious agents.207... 

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