Fucose linked

Fig. 15.3 Plant and mammalian N-glycans have different structures. As illustrated here, a core structure (in gray) is common to plant and mammalian biantennary complex N-glycans. However, differences in the glycan processing machineries in plants and in mammals result in the absence of sialic acids in the terminal position of the antennae and the presence of a bisecting p (1,2) -xylose and of an a(l,3)-fucose residue in PMPs instead of the a(l,6)-fucose linked to the proximal N-acetylglucos-amine of native mammalian N-glycans.

Specificity branched mannoses with fucose linked a(1,6) to the N- acetyl glucosamine,... 

The third generation andiracycline analogs with disaccharide, such as MEN 10755 (Figure 6) (44-46), possess a 2-deoxy fucose linked to the aglycon and... 

Fig. 2. Generalized structure of N-linked oligosaccharide of the pituitary glycoprotein hormones. SO = sulfate, GIcNAc = N — acetylglucosamine, GalNAc = N — acetylgalactosamine, Man = mannose, Fuc = fucose, SA = sialic (neuraminic) acid.

The primary cell walls of most higher plant species contain XGs of the XXXG type, which bear trisaccharide side chains (8) on the backbone [247]. The seeds of many plants contain XXXG-type XGs, in which about 30% of the xylose units possess a /3-D-Galp residue attached to position 2. Several plant species produce XGs that lack fucose and galactose, and have a-L-Ara/ attached to 0-2 of some of the Xylp side-chains, such as XG isolated from olive fruit [262] and soybean (Glycine maxima) meal [263]. However, a-L-Ara/ residues occur also 2-linked directly to some of the Glcp residues of the backbone [154]. 

Fucose Deoxyhexose Fuc GDP-Fuc May be external in both N- and 0-linked glycoproteins or internal, linked to the GIcNAc residue attached to Asn in N-linked species. Can also occur internally attached to the OH of Ser (eg, in t-PA and certain clotting factors). 

The glycosyl-linkage compositions of our three RG-II preparations were similar (Table 2) and corresponded to the relative sugar molar ratios obtained from compositional (TMS derivatives) analyses indicating that methylation was complete. Almost all the methyl ethers obtained could be attributed to known residues of the RG-II molecule (Figure 1) and our data were in accordance to that previously reported for RG-II from different plant origins [3,8,12,20,26]. The relative molar ratios of these "characteristic" methyl ethers (calculated on the basis of 1 residue of 3,4-linked fucose) were almost all in stoichiometric amounts (Table 3), confirming thus that our three preparations corresponded to the accepted model for RG-II. 

Relative molar ratios (calculated on the basis of 1 residue of 3,4-linked fucose) of methyl ethers characteristic for RG-II in the preparations isolated from fruit-derived products... 

The detected rhamnose residues were typical for the backbone of pectin. Some of the (l- 2)-linked a-L-rhamnopyranosyl residues were branched, having side chains attached to 0-4 and to 0-3. Additionally terminal and double branched rhamnose residues were found in small amounts. Fiiudly typical fucose and xylose residues were detected in all the analysed fractions. 

Tretter, V., Altmann, F. and Marz, L. (1991) Peptide-A74-(A-acetyl-P-glucosamiriyl) asparagine amidase F cannot release glycans with fucose attached al-3 to the asparagine-linked A-acetylglucosamin e residue. European Journal of Biochemistry 199, 647-652. 

Wilson, I.B.H., Harthill, J.E., Mullin, N.P., Ashford, D.A. and Altmann, F. (1998) Core al,3-fucose is a key part of the epitope recognized by antibodies reacting against plant JV-linked oligosaccharides and is present in a wide variety of plant extracts. Glycobiology 8, 651-661. 

The latter was isolated in the form of fully methylated methyl fuco-side, i. e., methyl 2,3,4-trimethyl-a-L-fucoside (XLVII), a compound previously obtained from methylated gum tragacanth.128 The recognition of this particular derivative indicates that the n-fucose residues in part at least must constitute end groups linked glycosidically to the rest of the molecule. The same compound128 was isolated by methylation and... 

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