A-Acetyllactosamine structures

An enzyme which transfers the a-Gal residue to A-acetyllactosamine structures in the glycoproteins of mammals other than humans has attracted attention because the a-Gal/)-(1 3)-Gal epitope is a major obstacle to the use of organs from other mammals in xenotransplantation because of the... 

Fig. 2. iV-glycans of the hybrid type. A triantennary structure with sialylated Af-acetyllactosamine (LacNAc) building blocks B biantennary structure with sialylated or fucosylated poly-LacNAc building blocks. The N-glycan core structure is written in bold letters... 

H Chemical Shifts of Structural-reporter Groups of Constituent Monosaccharides for Asialo Di-, Tri-, and Tetra-antennary Glycopeptides of the A-Acetyllactosamine Type (Compounds 8, 9, and 13)... 

Therefore, the simplest explanation for the action of a-lactalbumin and galactosyltransferase, as suggested by Browne et al. (1969), is that a-lactalbumin, in complexing with galactosyltransferase, modifies the conformational structure of the latter to produce a form of the enzyme that more readily catalyzes the production of lactose, and then does so in preference to A -acetyllactosamine. 

Rat mammary-gland transferrin. Rat milk transferrin contains four glycovari-ants that differ only in their sialic acid content. The primary structure of the two major variants has been determined by Escriva et al. [67]. As shown in Fig. 8D, the glycoforms contain either one or two A-acetylneuraminic acid residues a-2,6-linked to galactose in a conventional diantennary glycan of the A-acetyllactosaminic type. Most contain fucose a-l,6-linked to the proximal A-acetylglucosamine residue. 

The X-ray structure of a diantennary octasaccharide of the A-acetyllactosamine type complexed to isolectin I from Lathyrus ochrus at 2.3 A resolution was solved [53]. The complex is stabilized by numerous hydrogen bonds, many also involving water molecules. Van der Waals interactions, including some with aromatic residues are also involved. It is apparent that GlcNAc((3l-2)Man residues play an important role in the oligosaccharide-lectin interaction. 

---