N-acetyllactosamine residue

Carbohydrates of human STF are not fucosylated, while those of human LTF have an Q -l,6-fucose bound to the N-acetyl glucosamine residue linked to the peptide chain, and an o -l,3-fucose bound to the N -acetyllactosamine residues. 

The spectral characteristics of carbohydrate chains terminating in N-acetyllactosamine residues bearing NeuAc linked to Gal are summarized, for the a-(2- 6) and a-(2->3) type of linkage, respectively, in Tables XIII and XIV. 

N-acetylglucosamine, terminal a-N-acetyl-lactosamine and terminal N-Acetyllactosamine residues in glycoproteins Terminal mannose a(2-3)-linked sialic acid... 

Several fucosyltransferases have been isolated and used for in vitro synthesis. The Lewis A al,4-fucosyltransferase transfers unnatural fucose derivatives in from their GDP esters [23]. The enzyme al,3-fiicosyltransferase has been used to L-fucosylate the 3-position of the GlcNAc of A-acetyllactosamine and of sialyl a2,3-N-acetyllactosamine [24]. Several acceptor substrates with modifications in the GlcNAc residue could also be... 

Two well defined ways of terminating chains of the N-acetyllactosamine type by a NeuAc residue will be treated here, namely, (i) the a-(2—>6) and (it) the a-(2- 3) attachment of NeuAc to a Gal residue that forms part of an N-acetyllactosamine unit. First, the spectral features of structures containing only < -(2— 6)-linked NeuAc (compounds 21-34) will be discussed. Then, the characteristics and influences of NeuAc in a-(2->3) linkage to Gal will be considered (compounds 35-38). Finally, (Hi) some structures (compounds 39-41) possessing a-NeuAc(2— 6)Gal, as well as NeuAc(2- 3)Gal, will be the subjects of discussion. 

The chemical shifts of the structural-reporter groups of Fuc in a-(1—>2) linkage to Gal of an N-acetyllactosamine branch, together with the influences of its introduction upon the chemical-shift values of reporter groups of neighboring residues, are summarized in Table XXI. 

Compound 60 is a sialo glyco-asparagine of the N-acetyllactosamine type containing NeuAc in a-(2- 3) linkage to Gal-c. The latter residue forms part of an additional N-acetyllactosamine unit (b-c) which is /3-(1— 3)-linked to the fundamental structure (55). Compound 60 has been isolated from the urine of a patient with aspartylglucosaminuria89 as the major component of a mixture also containing small amounts of 58 and of the asialo analog of 60. The 500-MHz, H-n.m.r. spectrum of this mixture is presented in Fig. 43 the pertinent n.m.r.-spectral parameters of 60 are compiled in Table XXIII. 

The introduction of a (sialylated) N-acetyllactosamine unit /3-( 1—>3)-linked to Gal-a gives rise to very few alterations in chemical shifts, coupling constants, and line widths of structural-reporter groups of neighboring residues that can be used for the localization of additional N-acetyllactosamine units in more-complex structures (compare Refs. 91-92a). The influences of this unit are almost exclusively re-... 

The above situation has also been exemplified with recent findings in the galectin field, wherein lactose and N-acetyllactosamine derivatives 5 and 6 were showed to be I4x and 50x times more potent than their parent saccharides against galectin-3, respectively (Scheme 2). In the first case 14), compound 5 has its aglycone modified by an aromatic residue, while compound 6 (75),... 

Of the oligosaccharides examined for their capacity to inhibit WGA, only those containing 2-acetamido-2-deoxy-D-glucose residues proved effective. Lactose, cellobiose, cellotriose, and N-acetyllactosamine (2-acetamido-2-deoxy-4-0-/3-D-galactopyranosyl-D-glucose) were all inactive as inhibitors of the p-azophenyl 2-acetamido-2-deoxy-)8-D-glucopyranoside-bovine serum albumin-WGA reaction.498 Table IX presents representative inhibition data. 

The essential energy source is the enolpyruvate phosphate, a compound easily accessible in great quantities by chemical synthesis. Likewise, the source of the galactopyranosyl residue, the a-D-glucopyranosyl phosphate 10.56, is also accessible without problems. Nucleotides only play a catalytic role. In fact all the enzymes involved are active at pH 8 thus substrate and enzymes can be mixed in the same vessel and a cycle, to which the only nucleotide added is a catalytic amount of UDP Glc (2%, mol/mol), can be achieved. This cycle will manufacture N-acetyllactosamine following equation (10.14) until the substrates are all used (Fig. 10.4) (Wong et al. 1982). 

The o 3-Fuc-transferases have interesting differences in specificity toward their acceptor substrates. FUT3, 4, 5, and 6 act preferably on internal GlcNAc residues of N-acetyllactosamines as the substrate and are thus involved in the synthesis of internal or dimeric Lewis antigens. " FUT3, 5, and 6 act on both neutral... 

To illustrate the effect of sialic acid in higher-branched compounds of the N-acetyllactosamine type the asialo-triantenna is used as a reference. In the triantenna bearing three NeuSAc residues, a(2-6)-linked to Gal, the effects of sialylation of Gal 6 and 6 are similar to those observed in the corresponding diantenna. Compared with the spectrum of the diantenna the extra branch is... 

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