Glycosyl group

Transferases. Enzymes which transfer a group, possibly a methyl group or a glycosyl group, from one compound to another. The name of the group transferred is usually in-... 

The names of the individual compounds of this type are formed by replacing (a) the -ose of the systematic or trivial name of the aldose by -uronic acid , (b) the -oside of the name of the glycoside by -osiduronic acid or (c) the -osyl of the name of the glycosyl group by -osy luronic acid . The carbon atom of the (potential) aldehydic carbonyl group (not that of the carboxy group as in normal systematic nomenclature [13,14]) is numbered 1 (see 2-Carb-2.1, note 1). 

Transferases catalyze transfer of groups such as methyl or glycosyl groups from a donor molecule to an acceptor molecule. 

Compound Glycose residue Glycosyl group Glycosyl residue ... 

A. Marra, M.-C. Schermann, A. Dondoni, A. Casnati, P. Minari, and R. Ungaro, Sugar calixarenes Preparation of calix[4]arenes substituted at the lower and upper rims with O-glycosyl groups, Angew. Chem. Int. Ed., 33 (1994) 2479-2481. 

The majority of ascomycetous yeasts form cell-wall mannans or ga-lactomannans having main chains of (1— 6)-linked a-D-mannopyrano-syl residues, often substituted at 0-2 by a-linked glycosyl groups. The linkage types in the rest of the side chains vary widely, and can consist of 2-O-substituted a- or /3-D-mannopyranosyl residues, or 3-O-substi-... 

Transferring other glycosyl groups 3.1.11 Exodeoxyribonucleases producing 5 -... 

Transferring other glycosyl groups. Transferring alkyl or aryl groups, other than methyl groups. 

The generic term glycosides defines all mixed acetals formed by the acetalisation of the cyclic forms of aldoses and ketoses. Glycosyl groups are monosaccharides that have lost their anomeric -OH group the suffix -yl is used to indicate the change that has occurred at C-1. 

Disaccharides are named by adding the name of a glycosyl group as a prefix to that of the monosaccharide chosen as parent, as exemplified by a-lactose (a Haworth perspective formula and a conformational formula are shown). 

As mentioned earlier, glycosyl groups that are unique to plants, such as P(l,2)-xylose and core a(l,3)-fucose, are also responsible for increased allergenicity of plant-derived proteins. A number of approaches have been employed to circumvent this problem, and a few are mentioned here. 

FIGURE 5.1(b) Biosynthetic processing of A -glycans in the plant ER and Golgi. Each step indicates the glycosyl groups added to or modified on a nascent polypeptide and the enzymes responsible for this process. (Revised from Chen et al. (2005). Med. Res. Rev. 25(3), 343-360.)... 

The ion-exchange separation usually affords individual fractions of structurally related glycosyl esters of nucleoside pyrophosphates, containing the same nucleotide residue, but differing in the structure of the glycosyl groups. Separation of the esters of N-acetylhexos-amines, uronic acids, and neutral monosaccharides from one another is also usually achieved. 

The dependence between the reactivity of sugar nucleotides and the structure of the glycosyl group appears similar to that observed in simple glycosides, although the information available is very limited. For example, the a-D-galactopyranosyl and /J-D-glu-copyranosyl esters of adenosine 5 -pyrophosphate are cleaved more... 

The ability of the glycosyl esters of nucleoside pyrophosphates to undergo such degradation is strongly dependent upon the stereochemistry and conformation of the glycosyl group. 

Esters of /3-D-mannopyranosyl pyrophosphates have not yet been prepared, and consequently their behavior in alkaline solution is unknown. However, thymidine 5 -(/3-L-rhamnopyranosyl pyrophosphate), in which the steric disposition of groups should be similar in the normal (1C) conformation of the glycosyl group (85), is cleaved readily under alkaline conditions.103... 

It remains unclear whether or not the rate of cleavage of the gly-cosyl bond in sugar nucleotides depends upon the structure of the nucleotide residue, and the same uncertainty is true for other reactions that affect the glycosyl group no systematic kinetic studies have been reported. However, it may be noted that there appears to be no essential difference between the rates of acidic hydrolysis of the 5 -(a-D-glucopyranosyl pyrophosphates) of uridine and N3-methyluridine, 331... 

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